Fix code quality

osu.Game/Beatmaps/Drawables/StarRatingDisplay.cs

@@ -1,7 +1,6 @@
 // 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 System;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Extensions.Color4Extensions;
@@ -39,8 +38,6 @@ namespace osu.Game.Beatmaps.Drawables
 
         private readonly Bindable<double> displayedStars = new BindableDouble();
 
-        private readonly Container textContainer;
-
         /// <summary>
         /// The currently displayed stars of this display wrapped in a bindable.
         /// This bindable gets transformed on change rather than instantaneous, if animation is enabled.