Fix so can work without locale defined

If `FMT_STATIC_THOUSANDS_SEPARATOR` defined, then locale is not included or defined, so this call will be unresolved.  I think this is the correct fix based on the code in `format-inl.h` and `format.h`

include/fmt/ostream.h

@@ -93,7 +93,9 @@ void format_value(buffer<Char>& buf, const T& value,
                   locale_ref loc = locale_ref()) {
   formatbuf<Char> format_buf(buf);
   std::basic_ostream<Char> output(&format_buf);
+  #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
   if (loc) output.imbue(loc.get<std::locale>());
+  #endif
   output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
   output << value;
   buf.resize(buf.size());