fix: fixed plunger not initialized

lib/game/pinball_game.dart

@@ -95,7 +95,8 @@ class PinballGame extends Forge2DGame
   Future<void> _addPlunger() async {
     plunger = Plunger(
       compressionDistance: camera.viewport.effectiveSize.y / 12,
-    )..initialPosition = screenToWorld(
+    );
+    plunger.initialPosition = screenToWorld(
       Vector2(
         camera.viewport.effectiveSize.x / 1.035,
         camera.viewport.effectiveSize.y - plunger.compressionDistance,

test/game/components/plunger_test.dart

@@ -220,7 +220,6 @@ void main() {
     final flameTester = flameBlocTester(gameBloc: () => gameBloc);
 
     group('initializes with', () {
-      // FIXME(alestiago): Plunger not initialized error.
       flameTester.test(
         'plunger body as bodyA',
         (game) async {