[llvm] Add necessary permissions to release issue workflow (PR #79272)

[Nikita Popov via llvm-commits]

nikic wrote:

Unfortunately we still get a permission error. I think this is because we're using the wrong token to post the issue comment. I've opened https://github.com/llvm/llvm-project/pull/79300 to pass two separate tokens.

https://github.com/llvm/llvm-project/pull/79272