Update notes on super.onDragStart/End

doc/tutorials/klondike/step4.md

@@ -584,7 +584,8 @@ it so that it would check whether the card is allowed to be moved before startin
 
 We have also added a call to `super.onDragStart()` which sets an `_isDragged` variable to `true` 
 in the `DragCallbacks` mixin, we need to check this flag via the public `isDragged` getter in 
-the `onDragUpdate()` method. Let's also use `super.onDragEnd()` to set the flag back to `false`:
+the `onDragUpdate()` method and use `super.onDragEnd()` in `onDragEnd()` so the flag is set back
+to `false`:
 
 ```dart
   @override