Fix removing entire declaration

Fix removing the entire declaration because at line 999 there is one.
CI Error in macOS.

include/fmt/format.h

@@ -4025,10 +4025,6 @@ constexpr detail::udl_arg<wchar_t> operator"" _a(const wchar_t* s, size_t) {
 }
 }  // namespace literals
 #endif  // FMT_USE_USER_DEFINED_LITERALS
-
-namespace detail {
-extern template struct basic_data<void>;
-}  // namespace detail
 FMT_END_NAMESPACE
 
 #ifdef FMT_HEADER_ONLY