Docs: Refine changelog's README

Mention how changelogs are generated nowadays.

changelogs/README.md

 # Generating changelog entries
 
-To generate and validate your changelog entries:
+From GitLab 14.0.0 onwards, [CHANGELOG.md](../CHANGELOG.md) is generated
+by parsing [Git trailers](https://git-scm.com/docs/git-interpret-trailers)
+in commit messages.
 
-1. Run `bin/changelog` to generate.
-1. Run `yamllint changelogs` to validate.
-
-See [development/changelog] documentation for detailed usage.
-
-[development/changelog]: https://docs.gitlab.com/ee/development/changelog.html
+See [documentation](https://docs.gitlab.com/ee/development/changelog.html#how-to-generate-a-changelog-entry)
+on how to generate changelog entries.
 
 # Changelog archival