docs: Update Input docs (#3029)

site/docs/11-input/10.1-input.mdx

@@ -23,7 +23,7 @@ class Player extends ex.Actor {
       engine.input.keyboard.isHeld(ex.Input.Keys.W) ||
       engine.input.gamepads.at(0).getAxes(ex.Input.Axes.LeftStickY) > 0.5
     ) {
-      player._moveForward()
+      // implement the code to move the player forward
     }
   }
 }