pyup: Scheduled weekly dependency update for week 19 (#8170)
* Update virtualenv from 20.4.4 to 20.4.6
* Update django from 2.2.20 to 2.2.22
* Update sphinx from 3.5.4 to 4.0.0
* Update sphinx from 3.5.4 to 4.0.0
* Update django-vanilla-views from 2.0.0 to 3.0.0
* Update watchdog from 2.0.3 to 2.1.1
* Update tox from 3.23.0 to 3.23.1
* Update pytest from 6.2.3 to 6.2.4
* Update pytest-mock from 3.6.0 to 3.6.1
* Update docs' requirements
* Downgrade sphinx
* Update conf.py
Co-authored-by: Santos Gallegos <stsewd@protonmail.com>