Update urllib3 to 1.26.6

[pyup-bot]

This PR updates urllib3 from 1.26.4 to 1.26.6.

Changelog

1.26.5

-------------------

* Fixed deprecation warnings emitted in Python 3.10.
* Updated vendored ``six`` library to 1.16.0.
* Improved performance of URL parser when splitting
the authority component.

Links

• PyPI: https://pypi.org/project/urllib3
• Changelog: https://pyup.io/changelogs/urllib3/
• Docs: https://urllib3.readthedocs.io/

[pyup-bot]

Closing this in favor of #1689