Re-skip a condvar test

[StephanTLavavej]

After merging #4721, two CI runs sporadically failed with:

Assertion failed: test1 == 0, file D:\a\_work\1\s\llvm-project\libcxx\test\std\thread\thread.condition\thread.condition.condvar\notify_all.pass.cpp, line 35

Assertion failed: test2 == 0, file D:\a\_work\1\s\llvm-project\libcxx\test\std\thread\thread.condition\thread.condition.condvar\notify_all.pass.cpp, line 45

This test is bogus, so I've reported llvm/llvm-project#95944 upstream. It appears to be the only affected test.