[libc++] Fix incorrect guard against the presence of wide characters

[ldionne]

Summary

TEST_HAS_NO_WIDE_CHARACTERS should only be used in the tests.

[jloser]

LGTM!

[Mordante]

Nice catch, seems like a copy-paste bug. LGTM!

libcxx/include/__format/unicode.h

#    if _LIBCPP_STD_VER > 20
   }
 #    endif // _LIBCPP_STD_VER > 20
 
 private:
   const char* __first_;
   const char* __last_;
 };
 
-#    ifndef TEST_HAS_NO_WIDE_CHARACTERS
+#    ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 _LIBCPP_HIDE_FROM_ABI constexpr bool __is_surrogate_pair_high(wchar_t __value) {
   return __value >= 0xd800 && __value <= 0xdbff;
 }
 
 _LIBCPP_HIDE_FROM_ABI constexpr bool __is_surrogate_pair_low(wchar_t __value) {
   return __value >= 0xdc00 && __value <= 0xdfff;
 }
 
_LIBCPP_HIDE_FROM_ABI constexpr __consume_p2286_result __consume_p2286() noexcept {
     return {0, __result};
   }
 #      endif // _LIBCPP_STD_VER > 20
 
 private:
   const wchar_t* __first_;
   const wchar_t* __last_;
 };
-#    endif
+#    endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
 
 _LIBCPP_HIDE_FROM_ABI constexpr bool __at_extended_grapheme_cluster_break(
     bool& __ri_break_allowed,
     bool __has_extened_pictographic,
     __extended_grapheme_custer_property_boundary::__property __prev,
     __extended_grapheme_custer_property_boundary::__property __next) {
   using __extended_grapheme_custer_property_boundary::__property;