Cleanup pip installs

[markstur]

I don't see how dask is even used.
The other commented out ones were not needed by me, but are they useful?

[cdiep]

Agree that dask is not used in this notebook.

[cdiep]

As for the other system command calls (to install ibm-cos-sdk or watson-machine-learning-client ), they are useful for newly created COS or WML instances. However, it looks like watson-machine-learning-client is automatically included whenever a WML instance is created. Not sure about COS instances.