Have ExtUI::getProgress use ui.get_progress (#13328)

Marlin/src/lcd/extensible_ui/ui_api.cpp

   #endif
 
   uint8_t getProgress_percent() {
-    return IFSD(card.percentDone(), 0);
+    return ui.get_progress();
   }
 
   uint32_t getProgress_seconds_elapsed() {