pyup: Scheduled weekly dependency update for week 20 (#8186)
* Update django from 2.2.22 to 2.2.23
* Update sphinx from 4.0.0 to 4.0.1
* Update gitpython from 3.1.15 to 3.1.17
* Update django-permissions-policy from 4.0.0 to 4.0.1
* Update sphinx-tabs from 2.1.0 to 3.0.0
* Update pytest-django from 4.2.0 to 4.3.0
* Update pytest-cov from 2.11.1 to 2.12.0
* Unpin sphinx
Co-authored-by: Santos Gallegos <stsewd@protonmail.com>