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

[Baranov Victor via llvm-commits]

vbvictor wrote:

With this config, It's not a big deal. I will use format like in [this one](https://github.com/llvm/llvm-project/blob/main/libcxx/.clang-tidy).
But generally speaking, should LLVM-based tools used in development have the same policy as compilers or not? 

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