[llvm] [Github] Remove use of deprecated login_or_token (PR #172240)

[Baranov Victor via llvm-commits]

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

LGTM, deprecation note for context: https://pygithub.readthedocs.io/en/v1.59.0/changes.html

https://github.com/llvm/llvm-project/pull/172240