Make remains of TestSceneModSettings non-visual

As they're not really testing anything visual.

osu.Game.Tests/Mods/ModSettingsTest.cs

@@ -0,0 +1,36 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using NUnit.Framework;
+using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Osu.Mods;
+
+namespace osu.Game.Tests.Mods
+{
+    public class ModSettingsTest
+    {
+        [Test]
+        public void TestModSettingsUnboundWhenCopied()
+        {
+            var original = new OsuModDoubleTime();
+            var copy = (OsuModDoubleTime)original.DeepClone();
+
+            original.SpeedChange.Value = 2;
+
+            Assert.That(original.SpeedChange.Value, Is.EqualTo(2.0));
+            Assert.That(copy.SpeedChange.Value, Is.EqualTo(1.5));
+        }
+
+        [Test]
+        public void TestMultiModSettingsUnboundWhenCopied()
+        {
+            var original = new MultiMod(new OsuModDoubleTime());
+            var copy = (MultiMod)original.DeepClone();
+
+            ((OsuModDoubleTime)original.Mods[0]).SpeedChange.Value = 2;
+
+            Assert.That(((OsuModDoubleTime)original.Mods[0]).SpeedChange.Value, Is.EqualTo(2.0));
+            Assert.That(((OsuModDoubleTime)copy.Mods[0]).SpeedChange.Value, Is.EqualTo(1.5));
+        }
+    }
+}