[llvm] github-automation: Use a single comment for team mentions on pull requests (PR #66037)

[via llvm-commits]

cor3ntin wrote:

Could we replace `@` in the description by something else so that people don't get extra mentions?
all the bugzilla bugs have a CC fields that ping everyone in the issue, putting that in the description is noisy for some folks

https://github.com/llvm/llvm-project/pull/66037