Bump sphinx from 3.5.1 to 3.5.2

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.1 to 3.5.2.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.5.1...v3.5.2)

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

requirements-dev.txt

@@ -2,5 +2,5 @@ setuptools==54.0.0
 wheel==0.36.2
 twine==3.3.0
 unittest-xml-reporting==3.0.4
-sphinx==3.5.1
+sphinx==3.5.2
 sphinx-rtd-theme==0.5.1