Remove or pin use of a deprecated python package, google-cloud

[crwilcox]

https://github.com/experimental-berlin/image-processor/blob/master/requirements.txt#L5

This repository contains a setup.py or requirements.txt file that depends on
the google-cloud package. This package is deprecated. If you wish to continue
to use this package, please pin the version to google-cloud<0.34.0. If you have
more time to dedicate to this, I would advise sorting out which sub-packages you
actually rely on and depending on them.

For further information please view this package on PyPI, https://pypi.org/project/google-cloud/