chore(deps-dev): bump sphinx from 3.5.0 to 3.5.1

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.0 to 3.5.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.5.0...v3.5.1)

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

dev-requirements.txt

@@ -1,4 +1,4 @@
-Sphinx==3.5.0
+Sphinx==3.5.1
 sphinx-bootstrap-theme==0.7.1
 sphinxcontrib-fulltoc==1.2.0
 sphinxcontrib-websupport==1.2.4