Fix a few exception_wrapper tests under MSVC
Fix a few exception_wrapper tests under MSVC

Summary: They were incorrectly comparing against string literals rather than the actual demangled names. MSVC includes `class/struct` as part of the mangled name, so they also appear in the demangled name, in contrast to GCC/Clang, which don't.

Reviewed By: yfeldblum

Differential Revision: D5271087

fbshipit-source-id: 41fa0cebe098b1b935e1f8b1af5882c412cf6254

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