headers: Add a missed case of _CRT_INTERNAL_LOCAL_PRINTF_OPTIONS in _vscwprintf

Our _CRT_INTERNAL_LOCAL_PRINTF_OPTIONS define contains
_CRT_INTERNAL_PRINTF_LEGACY_WIDE_SPECIFIERS, which affects how
wide strings are formatted - so this should have a functional
effect, fixing an earlier inconsistency with this function.

Signed-off-by: Martin Storsjö <martin@martin.st>