Don't set refresh interval as user templates can no longer affect it

[rudolf]

Summary

Remove explicitly setting refresh_interval when migrations create or clone an index as this is not allowed on serverless. The refresh_interval was previously set explicitly to avoid user templates overriding the refresh interval to a value that effectively breaks Kibana.

User templates should not affect system indices, but when this feature was introduced in 8.4.0 an exception was made for Kibana because Kibana was still using a index template for the user sesssions index. See elastic/elasticsearch#98695 for more details.

Blocked on elastic/elasticsearch#98696

Checklist

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• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• Any UI touched in this PR is usable by keyboard only (learn more about keyboard accessibility)
• Any UI touched in this PR does not create any new axe failures (run axe in browser: FF, Chrome)
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
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• This was checked for cross-browser compatibility

Risk Matrix

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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
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

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)

[TinaHeiligers]

Approving pre-emptively to make the urgent change if needed.

[kibana-ci]

💚 Build Succeeded

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• Commit: 7f12ed7

Metrics [docs]

✅ unchanged

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[rudolf]

elastic/elasticsearch#98696 was reverted due to it breaking forward compatibility from Kibana 7.17

But the approach in #164850 is preferred anyway