Update Migrating.md

docs/Migrating.md

 
 ## Migrating from ML-Agents toolkit v0.5 to v0.6
 ### Important
-* Brains are now Scriptable Objects instead of Monobehaviors. This will
-  allow you to set Brains into prefabs and use the same brains accross 
+* Brains are now Scriptable Objects instead of MonoBehaviors. This will
+  allow you to set Brains into prefabs and use the same brains across 
   scenes.
 * To update a scene from v0.5 to v0.6, you must:
   *  Remove the `Brain` GameObjects in the scene