Update urllib3 to 1.26.15

[pyup-bot]

This PR updates urllib3 from 1.26.8 to 1.26.15.

Changelog

1.26.14

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

* Fixed parsing of port 0 (zero) returning None, instead of 0. (`2850 <https://github.com/urllib3/urllib3/issues/2850>`__)
* Removed deprecated getheaders() calls in contrib module. Fixed the type hint of ``PoolKey.key_retries`` by adding ``bool`` to the union. (`2865 <https://github.com/urllib3/urllib3/issues/2865>`__)

1.26.13

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

* Deprecated the ``HTTPResponse.getheaders()`` and ``HTTPResponse.getheader()`` methods.
* Fixed an issue where parsing a URL with leading zeroes in the port would be rejected
even when the port number after removing the zeroes was valid.
* Fixed a deprecation warning when using cryptography v39.0.0.
* Removed the ``<4`` in the ``Requires-Python`` packaging metadata field.

1.26.12

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

* Deprecated the `urllib3[secure]` extra and the `urllib3.contrib.pyopenssl` module.
Both will be removed in v2.x. See this `GitHub issue <https://github.com/urllib3/urllib3/issues/2680>`_
for justification and info on how to migrate.

1.26.11

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

* Fixed an issue where reading more than 2 GiB in a call to ``HTTPResponse.read`` would
raise an ``OverflowError`` on Python 3.9 and earlier.

1.26.10

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

* Removed support for Python 3.5
* Fixed an issue where a ``ProxyError`` recommending configuring the proxy as HTTP
instead of HTTPS could appear even when an HTTPS proxy wasn't configured.

1.26.9

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

* Changed ``urllib3[brotli]`` extra to favor installing Brotli libraries that are still
receiving updates like ``brotli`` and ``brotlicffi`` instead of ``brotlipy``.
This change does not impact behavior of urllib3, only which dependencies are installed.
* Fixed a socket leaking when ``HTTPSConnection.connect()`` raises an exception.
* Fixed ``server_hostname`` being forwarded from ``PoolManager`` to ``HTTPConnectionPool``
when requesting an HTTP URL. Should only be forwarded when requesting an HTTPS URL.

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 #41