Update urllib3 to 1.25.11

[pyup-bot]

This PR updates urllib3 from 1.25.10 to 1.25.11.

Changelog

1.25.11

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

* Fix retry backoff time parsed from ``Retry-After`` header when given
in the HTTP date format. The HTTP date was parsed as the local timezone
rather than accounting for the timezone in the HTTP date (typically
UTC) (Pull 1932, Pull 1935, Pull 1938, Pull 1949)

* Fix issue where an error would be raised when the ``SSLKEYLOGFILE``
environment variable was set to the empty string. Now ``SSLContext.keylog_file``
is not set in this situation (Pull 2016)

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 #1418