[clang] [clang][ASTMatchers] format ASTMatchers.h (PR #203766)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman requested changes to this pull request.

Is there a reason why the formatting is needed? Part of our developer policy is to not make these kinds of changes unless there's a reason because of the amount of problems it causes for downstreams due to merge conflicts. So it's not that we can't do it, it's that we want there to be a good reason. (If there is a reason for the change, I'd recommend updating the summary to explain them.)

https://github.com/llvm/llvm-project/pull/203766