refactor: simplified BezierCurveShape test

packages/pinball_flame/test/src/shapes/bezier_curve_shape_test.dart

@@ -5,21 +5,15 @@ import 'package:pinball_flame/pinball_flame.dart';
 
 void main() {
   group('BezierCurveShape', () {
-    late List<Vector2> controlPoints;
+    test('can be instantiated', () {
-
+      expect(
-    setUp(() {
+        BezierCurveShape(
-      controlPoints = [
+          controlPoints: [
             Vector2(0, 0),
             Vector2(10, 0),
             Vector2(0, 10),
             Vector2(10, 10),
-      ];
+          ],
-    });
-
-    test('can be instantiated', () {
-      expect(
-        BezierCurveShape(
-          controlPoints: controlPoints,
         ),
         isA<BezierCurveShape>,
       );