Removed unnecessary using directive

Sergio0694 · Sergio0694 · commit bca44b59ed60 · 2020-08-28T22:37:36.000+02:00
diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/UniformGrid/TakenSpotsReferenceHolder.cs b/Microsoft.Toolkit.Uwp.UI.Controls/UniformGrid/TakenSpotsReferenceHolder.cs
@@ -4,7 +4,6 @@
 
 using System.Collections;
 using System.Drawing;
-using System.Runtime.CompilerServices;
 using Microsoft.Toolkit.Diagnostics;
 
 namespace Microsoft.Toolkit.Uwp.UI.Controls
