chore(deps-dev): bump sphinx from 3.4.1 to 3.4.2

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.4.1 to 3.4.2.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.4.1...v3.4.2)

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

dev-requirements.txt

@@ -4,7 +4,7 @@ coveralls==2.2.0
 pytest==6.2.1
 pytest-cov==2.10.1
 attrs~=20.3.0
-Sphinx==3.4.1
+Sphinx==3.4.2
 sphinx-bootstrap-theme==0.7.1
 sphinxcontrib-fulltoc==1.2.0
 sphinxcontrib-websupport==1.2.4