[llvm] workflows: Automatically make backport requests from merged PRs (PR #126993)

[Tom Stellard via llvm-commits]

tstellar wrote:

For some reason the issue-release-workflow triggered on this:  https://github.com/llvm/llvm-project/actions/runs/13298256945/job/37134833231

https://github.com/llvm/llvm-project/pull/126993