Address MSVC C4686 in folly/lang/Pretty.h
Address MSVC C4686 in folly/lang/Pretty.h

Summary:
[Folly] Address MSVC C4686 in `folly/lang/Pretty.h`.

Resolves:

```
folly\lang\pretty.h(119): warning C4686: 'folly::detail::pretty_name_zarray<T>::zarray_': possible change in behavior, change in UDT return calling convention
```

Reviewed By: Orvid

Differential Revision: D14214290

fbshipit-source-id: c5e0ebd7c100413737bdcba157ec8b5ce42895de

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