[llvm] [workflows] Avoid usage of access token in issue-write.yml (PR #94011)

[Alexey Bader via llvm-commits]

https://github.com/bader approved this pull request.

Thanks!
I'm not an expert in GitHub Actions scripts, so it's better to get the feedback from @boomanaiden154.

https://github.com/llvm/llvm-project/pull/94011