fix: RemoveEffect should work within SequenceEffect (#2110)

Since the RemoveEffect was removing its parent and not its target it couldn't work within a SequenceEffect since it was just removing that effect instead.

packages/flame/lib/src/effects/remove_effect.dart

@@ -1,9 +1,8 @@
-import 'package:flame/src/effects/controllers/linear_effect_controller.dart';
-import 'package:flame/src/effects/effect.dart';
+import 'package:flame/effects.dart';
 
 /// This simple effect, when attached to a component, will cause that component
 /// to be removed from the game tree after `delay` seconds.
-class RemoveEffect extends Effect {
+class RemoveEffect extends ComponentEffect {
   RemoveEffect({
     double delay = 0.0,
     void Function()? onComplete,
@@ -15,7 +14,7 @@ class RemoveEffect extends Effect {
   @override
   void apply(double progress) {
     if (progress == 1) {
-      parent?.removeFromParent();
+      target.removeFromParent();
     }
   }
 }

packages/flame/test/effects/remove_effect_test.dart

@@ -1,6 +1,7 @@
 import 'package:flame/components.dart';
+import 'package:flame/effects.dart';
 import 'package:flame/game.dart';
-import 'package:flame/src/effects/remove_effect.dart';
+import 'package:flame_test/flame_test.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
@@ -41,5 +42,23 @@ void main() {
       game.update(0);
       expect(game.children.length, 0);
     });
+
+    testWithFlameGame('as a part of a sequence', (game) async {
+      final component = PositionComponent();
+      await game.ensureAdd(component);
+      component.add(
+        SequenceEffect([
+          MoveByEffect(Vector2.all(10), EffectController(duration: 1)),
+          RemoveEffect(),
+        ]),
+      );
+      game.update(0);
+      expect(game.children.length, 1);
+      game.update(0.5);
+      expect(game.children.length, 1);
+      game.update(1.0); // This completes the move effect
+      game.update(0); // This runs the remove effect
+      expect(game.children.length, 0);
+    });
   });
 }