Update validgpios.cpp

Author: hhvrc

src/serial/command_handlers/validgpios.cpp

@@ -20,7 +20,7 @@ static void handleValidGpios(std::string_view arg, bool isAutomated)
   for (std::size_t i = 0; i < pins.size(); i++) {
     if (pins[i]) {
       buffer.append(std::to_string(i));
-      buffer.append(",");
+      buffer.append(',');
     }
   }