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](https://github.com/sphinx-doc/sphinx/compare/v3.5.1...v3.5.2)

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

requirements-dev.txt

@@ -8,7 +8,7 @@ transifex-client==0.14.2
 selenium==3.141.0
 twine==3.3.0
 Pallets-Sphinx-Themes==1.2.3
-Sphinx==3.5.1
+Sphinx==3.5.2
 sphinx-issues==1.2.0
 sphinx-jinja==1.1.1
 sphinx-tabs==2.1.0