Move ShaderInstance finalizer around so DummyShaderInstance isn't finalized.

Maybe help a bit with test GC performance.

Robust.Client/Graphics/Clyde/Clyde.Shaders.cs

@@ -393,7 +393,18 @@ namespace Robust.Client.Graphics.Clyde
                 return new ClydeShaderInstance(newHandle, Parent);
             }
 
-            protected override void Dispose(bool disposing)
+            public override void Dispose()
+            {
+                Dispose(true);
+                GC.SuppressFinalize(this);
+            }
+
+            ~ClydeShaderInstance()
+            {
+                Dispose(false);
+            }
+
+            private void Dispose(bool disposing)
             {
                 Parent._deadShaderInstances.Enqueue(Handle);
             }

Robust.Client/Graphics/Shaders/ShaderInstance.cs

@@ -222,20 +222,10 @@ namespace Robust.Client.Graphics
             return DuplicateImpl();
         }
 
-        ~ShaderInstance()
+#pragma warning disable CA1816
+        public virtual void Dispose()
+#pragma warning restore CA1816
         {
-            Dispose(false);
-        }
-
-        public void Dispose()
-        {
-            Dispose(true);
-            GC.SuppressFinalize(this);
-        }
-
-        protected virtual void Dispose(bool disposing)
-        {
-            Disposed = true;
         }
 
         private void EnsureMutable()