Silence explicit case-fallthru

Firmware/mmu.cpp

@@ -1555,7 +1555,7 @@ void mmu_continue_loading(bool blocking)
         {
         case Ls::Enter:
             increment_load_fail();
-            // no break
+            // FALLTHRU
         case Ls::Retry:
             ++retry; // overflow not handled, as it is not dangerous.
             if (retry >= max_retry)

Firmware/ultralcd.cpp

@@ -2095,7 +2095,7 @@ if(lcd_clicked())
           {
           case FilamentAction::AutoLoad:
                eFilamentAction=FilamentAction::None; // i.e. non-autoLoad
-               // no break
+               // FALLTHRU
           case FilamentAction::Load:
                loading_flag=true;
                enquecommand_P(PSTR("M701"));      // load filament
@@ -7412,7 +7412,7 @@ bool lcd_selftest()
 			break;
 		case FanCheck::SwappedFan:
 			_swapped_fan = true;
-			// no break
+			// FALLTHRU
 		default:
 			_result = true;
 			break;
@@ -7435,7 +7435,7 @@ bool lcd_selftest()
 			break;
 		case FanCheck::SwappedFan:
 			_swapped_fan = true;
-			// no break
+			// FALLTHRU
 		default:
 			_result = true;
 			break;