update main readme

removed the Unity connect link as some folks were submitting issues there and getting lost.  we do not actively monitor the connect channel and do not want to cause confusion

README.md

 [contribution guidelines](CONTRIBUTING.md) and
 [code of conduct](CODE_OF_CONDUCT.md).
 
-You can connect with us and the broader community
-through Unity Connect and GitHub:
-
-* Join our
-  [Unity Machine Learning Channel](https://connect.unity.com/messages/c/035fba4f88400000)
-  to connect with others using the ML-Agents toolkit and Unity developers
-  enthusiastic about machine learning. We use that channel to surface updates
-  regarding the ML-Agents toolkit (and, more broadly, machine learning in
-  games).
-* If you run into any problems using the ML-Agents toolkit,
-  [submit an issue](https://github.com/Unity-Technologies/ml-agents/issues) and
-  make sure to include as much detail as possible.
+If you run into any problems using the ML-Agents toolkit,
+[submit an issue](https://github.com/Unity-Technologies/ml-agents/issues) and
+make sure to include as much detail as possible.
 
 For any other questions or feedback, connect directly with the ML-Agents
 team at ml-agents@unity3d.com.