Revert grid sizing to 576/640 per 2018 commit.

src/engine/Enum.java

@@ -2416,8 +2416,8 @@ public class Enum {
 
 	public enum CityBoundsType {
 
-		GRID(640),
-		ZONE(672),
+		GRID(576),
+		ZONE(640),
 		SIEGE(814);
 
 		public final float extents;