Update urllib3 to 1.26.8

[pyup-bot]

This PR updates urllib3 from 1.26.4 to 1.26.8.

Changelog

1.26.7

===================

* Fixed a bug with HTTPS hostname verification involving IP addresses and lack
of SNI. (Issue 2400)
* Fixed a bug where IPv6 braces weren't stripped during certificate hostname
matching. (Issue 2240)

1.26.6

===================

* Deprecated the ``urllib3.contrib.ntlmpool`` module. urllib3 is not able to support
it properly due to `reasons listed in this issue <https://github.com/urllib3/urllib3/issues/2282>`_.
If you are a user of this module please leave a comment.
* Changed ``HTTPConnection.request_chunked()`` to not erroneously emit multiple
``Transfer-Encoding`` headers in the case that one is already specified.
* Fixed typo in deprecation message to recommend ``Retry.DEFAULT_ALLOWED_METHODS``.

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 #1833