[llvm] format root clang-tidy config (NFC) (PR #147902)

[Carlos Galvez via llvm-commits]

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

LGTM. Worth noting is that the YAML list format is only supported since a few releases back, so it can break for users with older clang-tidy.

https://github.com/llvm/llvm-project/pull/147902