Remove all RequiredTypes usages

osu.Game.Tests/Visual/UserInterface/TestSceneButtonSystem.cs

@@ -2,7 +2,6 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using NUnit.Framework;
 using osu.Framework.Graphics;
@@ -17,13 +16,6 @@ namespace osu.Game.Tests.Visual.UserInterface
     [TestFixture]
     public class TestSceneButtonSystem : OsuTestScene
     {
-        public override IReadOnlyList<Type> RequiredTypes => new[]
-        {
-            typeof(ButtonSystem),
-            typeof(ButtonArea),
-            typeof(Button)
-        };
-
         private OsuLogo logo;
         private ButtonSystem buttons;