Update pip to 20.2.3

[pyup-bot]

This PR updates pip from 20.2.2 to 20.2.3.

Changelog

20.2.3

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

Deprecations and Removals
-------------------------

- Deprecate support for Python 3.5 (`8181 <https://github.com/pypa/pip/issues/8181>`_)

Features
--------

- Make the ``setup.py install`` deprecation warning less noisy. We warn only
when ``setup.py install`` succeeded and ``setup.py bdist_wheel`` failed, as
situations where both fails are most probably irrelevant to this deprecation. (`8752 <https://github.com/pypa/pip/issues/8752>`_)

Links

• PyPI: https://pypi.org/project/pip
• Changelog: https://pyup.io/changelogs/pip/
• Homepage: https://pip.pypa.io/