Simplify daily sink filename creation

include/spdlog/sinks/daily_file_sink.h

@@ -30,10 +30,7 @@ struct daily_filename_calculator
     {
         filename_t basename, ext;
         std::tie(basename, ext) = details::file_helper::split_by_extension(filename);
-        std::conditional<std::is_same<filename_t::value_type, char>::value, memory_buf_t, fmt::wmemory_buffer>::type w;
-        fmt::format_to(
-            w, SPDLOG_FILENAME_T("{}_{:04d}-{:02d}-{:02d}{}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1, now_tm.tm_mday, ext);
-        return fmt::to_string(w);
+		return fmt::format(SPDLOG_FILENAME_T("{}_{:04d}-{:02d}-{:02d}{}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1, now_tm.tm_mday, ext);        
     }
 };