♻️ Leverage 'IsWalking' function for monster walking checks

Source/monster.cpp

@@ -4189,7 +4189,7 @@ void GolumAi(int i)
 
 	if (golem._mmode == MM_DEATH
 	    || golem._mmode == MM_SPSTAND
-	    || (golem._mmode >= MM_WALK && golem._mmode <= MM_WALK3)) {
+	    || golem.IsWalking()) {
 		return;
 	}
 

Source/sync.cpp

@@ -172,7 +172,7 @@ void SyncMonster(int pnum, const TSyncMonster *p)
 	}
 
 	if (monster.position.tile.WalkingDistance({ p->_mx, p->_my }) <= 2) {
-		if (monster._mmode < MM_WALK || monster._mmode > MM_WALK3) {
+		if (!monster.IsWalking()) {
 			Direction md = GetDirection(monster.position.tile, { p->_mx, p->_my });
 			if (DirOK(ndx, md)) {
 				M_ClearSquares(ndx);