Remove DCO workflow in favor of DCO app. (#112)

Signed-off-by: Daniel (dB.) Doubrovkine <dblock@amazon.com>

CONTRIBUTING.md

@@ -82,15 +82,19 @@ By making a contribution to this project, I certify that:
     involved.
  ```
 
-We require that every contribution to OpenSearch is signed with a Developer Certificate of Origin. Additionally, please use your real name. We do not accept anonymous contributors nor those utilizing pseudonyms.
+We require that every contribution to OpenSearch is signed with a Developer Certificate of Origin. DCO checks are enabled via a [DCO workflow app](https://github.com/apps/dco) across the entire opensearch-project organization, and your PR will fail CI without it.
+
+Additionally, we kindly ask you to use your real name. We do not accept anonymous contributors, nor those utilizing pseudonyms.
 
 Each commit must include a DCO which looks like this
 
 ```
 Signed-off-by: Jane Smith <jane.smith@email.com>
 ```
 
-You may type this line on your own when writing your commit messages. However, if your user.name and user.email are set in your git configs, you can use `-s` or `– – signoff` to add the `Signed-off-by` line to the end of the commit message.
+You may type this line on your own when writing your commit messages. However, if your `user.name` and `user.email` are set in your `git config`, you can use `-s` or `––signoff` to add the `Signed-off-by` line to the end of the commit message automatically.
+
+Forgot to add DCO to a commit? Amend it with `git commit --amend -s`. 
 
 ## License Headers
 

RESPONSIBILITIES.md

@@ -9,7 +9,6 @@
   - [Maintain Overall Health of the Repo](#maintain-overall-health-of-the-repo)
   - [Manage Roadmap](#manage-roadmap)
   - [Add Continuous Integration Checks](#add-continuous-integration-checks)
-    - [Developer Certificate of Origin Workflow](#developer-certificate-of-origin-workflow)
   - [Use Semver](#use-semver)
   - [Release Frequently](#release-frequently)
   - [Promote Other Maintainers](#promote-other-maintainers)
@@ -73,10 +72,6 @@ Ensure the repo highlights features that should be elevated to the project roadm
 
 Add integration checks that validate pull requests and pushes to ease the burden on Pull Request reviewers.
 
-#### Developer Certificate of Origin Workflow
-
-Validates pull requests commits are all signed with DCO, [dco.yml](./workflow/dco.yml).  Example [pull request](https://github.com/opensearch-project/opensearch-ci/pull/16).
-
 ### Use Semver
 
 Use and enforce [semantic versioning](https://semver.org/) and do not let breaking changes be made outside of major releases.