[libcxx-commits] [libcxx] [libc++] Remove invalid char_traits instantiations from a test (PR #142016)

[A. Jiang via libcxx-commits]

https://github.com/frederick-vs-ja approved this pull request.

Specializations for `unsigned short` look quite MSVC-ish, but they seemed existing since the initial commit.
I think it's perfectly fine to remove them. Even when testing non-conforming mode of MSVC (`wchar_t` being `unsigned short`), the coverage should have been complete.

https://github.com/llvm/llvm-project/pull/142016