Update testinfra to 6.0.0

[pyup-bot]

This PR updates testinfra from 5.3.1 to 6.0.0.

Changelog

6.0.0

=====

* Breaking change: testinfra has moved to the https://github.com/pytest-dev/
organization. Project on PyPi is renamed as pytest-testinfra. A dummy
testinfra will make the transition, but you should rename to pytest-testinfra
in your requirements files.

Links

• PyPI: https://pypi.org/project/testinfra
• Changelog: https://pyup.io/changelogs/testinfra/
• Repo: https://github.com/philpep/testinfra