[libcxx-commits] [libcxx] [libc++][NFC] Avoid opening namespace std in the tests (PR #94160)

[Stephan T. Lavavej via libcxx-commits]

StephanTLavavej wrote:

This will make it easier for MSVC's STL to consume the `variant` and `optional` tests, thank you! :heart_eyes_cat:

https://github.com/llvm/llvm-project/pull/94160