Bump sphinx from 3.5.4 to 4.0.2

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.4 to 4.0.2.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.5.4...v4.0.2)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

poetry.lock

@@ -45,11 +45,11 @@ coverage = {extras = ["toml"], version = "^5.3"}
 pytest-django = "^4.1.0"
 pygments = "^2.7.4"
 xdoctest = "^0.15.0"
-sphinx = "^3.4.3"
+sphinx = "^4.0.2"
 sphinx-autobuild = "^2020.9.1"
 darglint = "^1.5.8"
 flake8-docstrings = "^1.5.0"
-flake8-rst-docstrings = "^0.0.14"
+flake8-rst-docstrings = "^0.2.3"
 pep8-naming = "^0.11.1"
 pre-commit-hooks = "^3.4.0"
 typeguard = "^2.10.0"