[9.0] (backport #18304) add release notes 9.0.6

[mergify]

Release notes for 9.0.6 and missing 9.0.5.

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This is an automatic backport of pull request #18304 done by Mergify.

[mergify]

Cherry-pick of b0fa923 has failed:

On branch mergify/bp/9.0/pr-18304
Your branch is up to date with 'origin/9.0'.

You are currently cherry-picking commit b0fa9238.
  (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/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/release-notes/index.md

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

[github-actions]

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Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[rubvs]

Similar to #17586, should skip backports for 9.0