feat: removed adding slinghsots

lib/game/pinball_game.dart

@@ -42,19 +42,9 @@ class PinballGame extends Forge2DGame
     await add(BottomWall(this));
     addContactCallback(BottomWallBallContactCallback());
 
-    unawaited(_addSlingShots());
     unawaited(_addFlippers());
   }
 
-  Future<void> _addSlingShots() async {
-    // TODO(alestiago): Change to the design position.
-    await add(
-      SlingShot(
-        position: ballStartingPosition + Vector2(0, 15),
-      ),
-    );
-  }
-
   Future<void> _addFlippers() async {
     const spaceBetweenFlippers = 2;
     final leftFlipper = Flipper.left(