fix: fixed plunger not initialized

lib/game/pinball_game.dart

@@ -95,12 +95,13 @@ class PinballGame extends Forge2DGame
   Future<void> _addPlunger() async {
     plunger = Plunger(
       compressionDistance: camera.viewport.effectiveSize.y / 12,
-    )..initialPosition = screenToWorld(
-        Vector2(
-          camera.viewport.effectiveSize.x / 1.035,
-          camera.viewport.effectiveSize.y - plunger.compressionDistance,
-        ),
-      );
+    );
+    plunger.initialPosition = screenToWorld(
+      Vector2(
+        camera.viewport.effectiveSize.x / 1.035,
+        camera.viewport.effectiveSize.y - plunger.compressionDistance,
+      ),
+    );
 
     await add(plunger);
   }

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 {