Hyperopt: Update networkx requirement to >=2.2

[optroodt]

networkx was pinned to version 2.2 because of Python 2.7 build issues (https://github.com/hyperopt/hyperopt/pull/506). Python 2.7 is now EOL and PyPI does not contain networkx versions greater than 2.2 for Python 2.7.

Version 2.2 is ~1.5 years old and people using Python 3.x (me) will probably want a newer version because of version conflicts with more modern packages (e.g. dbt).

Thus, can the requirement for networkx become networkx>=2.2 in order to satisfy both Python 2.7 and Python 3.x users?

[thomasburgess]

Bump.

[maxpumperla]

@optroodt sure, please send a PR

[optroodt]

There you go! :)

[kenbr7613]

When will this change be released to pypi?