Fix incorrect instruction to call node during 2D tutorial

getting_started/first_2d_game/05.the_main_game_scene.rst

@@ -198,7 +198,7 @@ Note that a new instance must be added to the scene using ``add_child()``.
         var mob = mob_scene.instantiate()
 
         # Choose a random location on Path2D.
-        var mob_spawn_location = get_node("MobPath/MobSpawnLocation")
+        var mob_spawn_location = $MobPath/MobSpawnLocation
         mob_spawn_location.progress_ratio = randf()
 
         # Set the mob's direction perpendicular to the path direction.