Bump sphinx from 2.3.1 to 2.4.1

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 2.3.1 to 2.4.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/2.0/CHANGES)
- [Commits](sphinx-doc/sphinx@v2.3.1...v2.4.1)

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

Author: dependabot-preview[bot]

dev-requirements.txt

@@ -3,7 +3,7 @@
 PyYAML==5.3
 Pygments==2.5.2
 Sphinx-Substitution-Extensions==2019.12.28.0
-Sphinx==2.3.1
+Sphinx==2.4.1
 VWS-Python-Mock==2019.12.27.0
 VWS-Test-Fixtures==2019.12.13.1
 autoflake==1.3.1