Bump sphinx from 2.4.4 to 3.0.3

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 2.4.4 to 3.0.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v2.4.4...v3.0.3)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: jalogisch

requirements.txt

@@ -23,7 +23,7 @@ requests==2.23.0
 singledispatch==3.4.0.3
 six==1.14.0
 snowballstemmer==2.0.0
-Sphinx==3.0.2
+Sphinx==3.0.3
 sphinx-autobuild==0.7.1
 sphinx-rtd-theme==0.4.3
 tornado==6.0.4