refactor: remove unused using

Author: ikpil

src/Box2D.NET.Samples/Samples/Issues/ShapeCastChain.cs

@@ -2,12 +2,8 @@
 // SPDX-FileCopyrightText: 2025 Ikpil Choi([email protected])
 // SPDX-License-Identifier: MIT
 
-using System.Numerics;
-using Box2D.NET.Shared;
-using ImGuiNET;
 using Silk.NET.GLFW;
 using static Box2D.NET.B2Ids;
-using static Box2D.NET.B2Hulls;
 using static Box2D.NET.B2Geometries;
 using static Box2D.NET.B2Types;
 using static Box2D.NET.B2MathFunction;

src/Box2D.NET.Samples/Samples/Stackings/CapsuleStack.cs

@@ -11,7 +11,7 @@ namespace Box2D.NET.Samples.Samples.Stackings;
 
 public class CapsuleStack : Sample
 {
-    private static int SampleCapsuleStack = SampleFactory.Shared.RegisterSample("Stacking", "Capsule Stack", Create);
+    private static readonly int SampleCapsuleStack = SampleFactory.Shared.RegisterSample("Stacking", "Capsule Stack", Create);
 
     struct Event
     {