[DOCS] Trim down PR template (elastic#198617)

## Summary

The existing PR template is rarely used. 

It is unclear if contributors actually verify what should be verified.

At the same time, the template is verbose and includes checks that can
be validated in other ways.

By trimming down the template, and removing the optional language from
the checks, we may strike a better balance of ensuring contributors
actually _complete_ the checklist.


### Checklist

Delete any items that are not applicable to this PR.

- ~[ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)~
- ~[ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials~
- ~[ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios~
- ~[ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed~
- ~[ ] Any UI touched in this PR is usable by keyboard only (learn more
about [keyboard
accessibility](https://webaim.org/techniques/keyboard/))~
- ~[ ] Any UI touched in this PR does not create any new axe failures
(run axe in browser:
[FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/),
[Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))~
- ~[ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)~
- ~[ ] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))~
- ~[ ] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)~


### Risk Matrix

Delete this section if it is not applicable to this PR.

Before closing this PR, invite QA, stakeholders, and other developers to
identify risks that should be tested prior to the change/feature
release.

When forming the risk matrix, consider some of the following examples
and how they may potentially impact the change:

| Risk | Probability | Severity | Mitigation/Notes |

|---------------------------|-------------|----------|-------------------------|
| By removing some checks, a PR may be | Low | Low | The test suite,
review process, and release processes should primarily ensure that the
PR is working as intended |
| By removing the optional language, contributor may get more frustrated
having to fill out boilerplate | Mid | Low | The template is
considerably shorted now |



### For maintainers

- [x] This was checked for breaking API changes and was [labeled
appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#_add_your_labels)
- [x] This will appear in the **Release Notes** and follow the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

---------

Co-authored-by: Brandon Kobel <brandon.kobel@gmail.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,37 +5,26 @@ Summarize your PR. If it involves visual changes include a screenshot or gif.
 
 ### Checklist
 
-Delete any items that are not applicable to this PR.
+Check the PR satisfies following conditions. 
+
+Reviewers should verify this PR satisfies this list as well.
 
 - [ ] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
 - [ ] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials
 - [ ] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios
-- [ ] [Flaky Test Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was used on any tests changed
-- [ ] Any UI touched in this PR is usable by keyboard only (learn more about [keyboard accessibility](https://webaim.org/techniques/keyboard/))
-- [ ] Any UI touched in this PR does not create any new axe failures (run axe in browser: [FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/), [Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))
 - [ ] If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the [docker list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
-- [ ] This renders correctly on smaller devices using a responsive layout. (You can test this [in your browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
-- [ ] This was checked for [cross-browser compatibility](https://www.elastic.co/support/matrix#matrix_browsers)
-
-
-### Risk Matrix
-
-Delete this section if it is not applicable to this PR.
+- [ ] This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The `release_note:breaking` label should be applied in these situations.
+- [ ] [Flaky Test Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was used on any tests changed
+- [ ] The PR  description includes the appropriate Release Notes section, and the correct `release_node:*` label is applied per the [guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
 
-Before closing this PR, invite QA, stakeholders, and other developers to identify risks that should be tested prior to the change/feature release.
+### Identify risks
 
-When forming the risk matrix, consider some of the following examples and how they may potentially impact the change:
+Does this PR introduce any risks? For example, consider risks like hard to test bugs, performance regression, potential of data loss.
 
-| Risk                      | Probability | Severity | Mitigation/Notes        |
-|---------------------------|-------------|----------|-------------------------|
-| Multiple Spaces—unexpected behavior in non-default Kibana Space. | Low | High | Integration tests will verify that all features are still supported in non-default Kibana Space and when user switches between spaces. |
-| Multiple nodes—Elasticsearch polling might have race conditions when multiple Kibana nodes are polling for the same tasks. | High | Low | Tasks are idempotent, so executing them multiple times will not result in logical error, but will degrade performance. To test for this case we add plenty of unit tests around this logic and document manual testing procedure. |
-| Code should gracefully handle cases when feature X or plugin Y are disabled. | Medium | High | Unit tests will verify that any feature flag or plugin combination still results in our service operational. |
-| [See more potential risk examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx) |
+Describe the risk, its severity, and mitigation for each identified risk. Invite stakeholders and evaluate how to proceed before merging.
 
+- [ ] [See some risk examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx)
+- [ ] ...
 
-### For maintainers
 
-- [ ] This was checked for breaking API changes and was [labeled appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#_add_your_labels)
-- [ ] This will appear in the **Release Notes** and follow the [guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)