[9.0](backport #5492) Add ingest-docs team as CODEOWNERS for release notes and docset.yml

[mergify]

Related to #5374

Adds ingest-docs team as CODEOWNERS for docs/release-notes and docset.yml. I think someone with admin access in this repo will need to add the @elastic/ingest-docs team with write access.

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This is an automatic backport of pull request #5492 done by Mergify.

[mergify]

Cherry-pick of 461aa39 has failed:

On branch mergify/bp/9.0/pr-5492
Your branch is up to date with 'origin/9.0'.

You are currently cherry-picking commit 461aa39.
  (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)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/CODEOWNERS

no changes added to commit (use "git add" and/or "git commit -a")

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

[prodsecmachine]

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[karenzone]

Close without merge