Bump sphinx from 3.5.3 to 3.5.4

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.3 to 3.5.4.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](https://github.com/sphinx-doc/sphinx/commits/v3.5.4)

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

requirements.txt

@@ -10,5 +10,5 @@ gunicorn==20.1.0
 pycodestyle==2.7.0
 pydocstyle==6.0.0
 requests==2.25.1
-Sphinx==3.5.3
+Sphinx==3.5.4
 Werkzeug==1.0.1