fix entry point typo (#306)

minigrid/__init__.py

@@ -65,7 +65,7 @@ def register_minigrid_envs():
 
     register(
         id="MiniGrid-SimpleCrossingS11N5-v0",
-        entry_point="gym_minigrid.envs:CrossingEnv",
+        entry_point="minigrid.envs:CrossingEnv",
         kwargs={"size": 11, "num_crossings": 5, "obstacle_type": Wall},
     )