[clang-tools-extra] [clang-tidy] Allow use of decltype(nullptr) for defining nullptr_t (PR #231637)

[Aiden Grossman via cfe-commits]

boomanaiden154 wrote:

> FWIW I don't think we need to modify clang-tidy to avoid warning just for libc++. We can just suppress the warning. We already have similar annotations to suppress unique_ptr warnings inside the unique_ptr implementation IIRC.

We don't need to, but given the fix is pretty simple, I don't think it hurts.

https://github.com/llvm/llvm-project/pull/231637