[main](backport #43432) docs: Prepare Changelog for 8.17.4

[mergify]

Prepare Changelog for 8.17.4.

Merge once the BC that will be published is decided.

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This is an automatic backport of pull request #43432 done by Mergify.

[mergify]

Cherry-pick of d6cb6e4 has failed:

On branch mergify/bp/main/pr-43432
Your branch is up to date with 'origin/main'.

You are currently cherry-picking commit d6cb6e488.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.next.asciidoc
	modified:   libbeat/docs/release.asciidoc

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally