[llvm] [Github][CI] Add note about AI tools in good-first-issue text (PR #173109)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 approved this pull request.

LGTM with Reid's adjustments. It would probably be good if someone else can approve before landing though.

https://github.com/llvm/llvm-project/pull/173109