Removing old python notebooks that were ported to normal python files in Sphinx docs (too different to preserve history). (#920)

Summary:
Pull Request resolved: #920

Removing original notebook examples as they were copied/modified by the docs team into normal python files and Sphynx docs at docs/source/examples.  The formats of these varied too much to go back and try to preserve history.

Reviewed By: shayne-fletcher

Differential Revision: D80534400

fbshipit-source-id: 07fa524133800b5903b40617f6569419e22dcccd

Author: johnwhumphreys