make everything use new difficulty system

objects/enemy/rolling_fiend.gd

@@ -22,9 +22,8 @@ func _ready():
 		if is_on_surface(DIRS[i]):
 			floor_direction = i
 			break
-	#Easy mode
-	if Game.is_easy_mode:
-		move_speed *= Game.easy_mode_speed_factor
+	# adjust to difficulty
+	move_speed *= Game.enemy_speed_factor
 
 func _physics_process(delta):
 	movement_accumulator += move_speed * delta