[llvm] [workflows] Add a job for requesting a release note on release branch PRs (PR #91826)

[via llvm-commits]

llvmbot wrote:

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Failed to cherry-pick: c99d1156c28dfed67a8479dd97608d1f0d6cd593)

https://github.com/llvm/llvm-project/actions/runs/9071247831

Please manually backport the fix and push it to your github fork.  Once this is done, please create a [pull request](https://github.com/llvm/llvm-project/compare)

https://github.com/llvm/llvm-project/pull/91826