Do not use the map's rules when rendering the minimap in the map chooser

Using the mod's rules is *a lot* faster because we don't have to load
each map's rules.

OpenRA.Editor/MapSelect.cs

@@ -76,7 +76,7 @@ namespace OpenRA.Editor
 				try
 				{
 					var tileset = Program.Rules.TileSets[map.Tileset];
-					MiniMapBox.Image = Minimap.AddStaticResources(tileset, map, Minimap.TerrainBitmap(tileset, map, true));
+					MiniMapBox.Image = Minimap.RenderMapPreview(tileset, map, true);
 				}
 				catch (Exception ed)
 				{