Removed unused using directives.

OpenRA.Game/Map/Map.cs

@@ -18,7 +18,6 @@ using System.Linq;
 using System.Reflection;
 using System.Text;
 using OpenRA.FileSystem;
-using OpenRA.Graphics;
 using OpenRA.Primitives;
 using OpenRA.Support;
 using OpenRA.Traits;

OpenRA.Game/Map/MapPreview.cs

@@ -11,7 +11,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Drawing;
 using System.IO;