Remove PathHash

This is 9(!) years old and we haven't had
pathfinding-related desyncs in quite a while.

We can still bring this back later if we ever
need it again.

OpenRA.Mods.Common/Traits/Mobile.cs

@@ -217,9 +217,6 @@ namespace OpenRA.Mods.Common.Traits
 		[Sync]
 		public CPos ToCell => toCell;
 
-		[Sync]
-		public int PathHash;	// written by Move.EvalPath, to temporarily debug this crap.
-
 		public Locomotor Locomotor { get; private set; }
 
 		public IPathFinder Pathfinder { get; private set; }