Update django to 2.2.3

[pyup-bot]

This PR updates django from 2.2.2 to 2.2.3.

Changelog

2.2.3

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

*Expected July 1, 2019*

Django 2.2.3 fixes several bugs in 2.2.2. Also, the latest string translations
from Transifex are incorporated.

Bugfixes
========

* Fixed a regression in Django 2.2 where :class:`~django.db.models.Avg`,
:class:`~django.db.models.StdDev`, and :class:`~django.db.models.Variance`
crash with ``filter`` argument (:ticket:`30542`).

* Fixed a regression in Django 2.2.2 where auto-reloader crashes with
``AttributeError``, e.g. when using ``ipdb`` (:ticket:`30588`).


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

Links

• PyPI: https://pypi.org/project/django
• Changelog: https://pyup.io/changelogs/django/
• Homepage: https://www.djangoproject.com/

[pyup-bot]

Closing this in favor of #152