Fix typo in Reward Signals docs (#3420)

docs/Reward-Signals.md

 
 #### Demo Path
 
-`demo_path` is the path to your `.demo` file or directory of `.demo` files. See the [imitation learning guide]
-(Training-Imitation-Learning.md).
+`demo_path` is the path to your `.demo` file or directory of `.demo` files. See the [imitation learning guide](Training-Imitation-Learning.md).
 
 #### (Optional) Encoding Size