Bump sphinx from 3.2.1 to 3.3.0 (#312)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.2.1 to 3.3.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.2.1...v3.3.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-dev.txt

@@ -2,5 +2,5 @@ setuptools==50.3.2
 wheel==0.35.1
 twine==3.2.0
 unittest-xml-reporting==3.0.4
-sphinx==3.2.1
+sphinx==3.3.0
 sphinx-rtd-theme==0.5.0