PFW-1454 Send button to MMU on MMU SELFTEST FAILED screen

Fixes an issue where the button on the MMU error screen doesn't do anything
when MMU SELFTEST FAILED is rendered

Firmware/mmu2_error_converter.cpp

@@ -255,7 +255,11 @@ Buttons ButtonAvailable(uint16_t ec) {
     case ERR_ELECTRICAL_PULLEY_TMC_DRIVER_SHORTED:
     case ERR_ELECTRICAL_SELECTOR_TMC_DRIVER_SHORTED:
     case ERR_ELECTRICAL_IDLER_TMC_DRIVER_SHORTED:
-        
+
+    case ERR_ELECTRICAL_PULLEY_SELFTEST_FAILED:
+    case ERR_ELECTRICAL_SELECTOR_SELFTEST_FAILED:
+    case ERR_ELECTRICAL_IDLER_SELFTEST_FAILED:
+
     case ERR_CONNECT_MMU_NOT_RESPONDING:
     case ERR_CONNECT_COMMUNICATION_ERROR: