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

[Tom Stellard via llvm-commits]

tstellar wrote:

> @tstellar Is there another advantage to having this upstream rather than just documenting somewhere what tokens need to be setup/with what permissions for the workflows to work?

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


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