pathfinder: fix typo in rustg_remove_node_astar (tgstation#162)

Author: vvvv-vvvv

dmsrc/pathfinder.dm

@@ -21,10 +21,10 @@
  */
 #define rustg_add_node_astar(json) RUSTG_CALL(RUST_G, "add_node_astar")(json)
 
-/**²
+/**
  * Remove every link to the node with unique_id. Replace that node by null
  */
-#define rustg_remove_node_astart(unique_id) RUSTG_CALL(RUST_G, "remove_node_astar")(unique_id)
+#define rustg_remove_node_astar(unique_id) RUSTG_CALL(RUST_G, "remove_node_astar")(unique_id)
 
 /**
  * Compute the shortest path between start_node and goal_node using A*. Heuristic used is simple geometric distance