[llvm] [GitHub][workflows] Ask reviewers to merge PRs when author can not (PR #81142)

[David Spickett via llvm-commits]

DavidSpickett wrote:

https://github.com/PyGithub/PyGithub/pull/881/files if you want to see the details of the API call.

https://github.com/llvm/llvm-project/pull/81142