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

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> The advantage for upstream is that it's one less secret for us to maintain.

> And also composite actions don't have access to secrets, so if you want to download an artifact in a composite action you need to add an extra parameter for the secret.

Makes sense. It would be nice if Github would allow this in the upstream action, but maybe the security argument there makes sense.

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