Bump sphinx-substitution-extensions from 2020.7.4.1 to 2020.9.30.0

Bumps [sphinx-substitution-extensions](https://github.com/adamtheturtle/sphinx-substitution-extensions) from 2020.7.4.1 to 2020.9.30.0.
- [Release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases)
- [Changelog](https://github.com/adamtheturtle/sphinx-substitution-extensions/blob/master/CHANGELOG.rst)
- [Commits](adamtheturtle/sphinx-substitution-extensions@2020.07.04.1...2020.09.30.0)

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

Author: dependabot-preview[bot]

dev-requirements.txt

@@ -1,5 +1,5 @@
 PyYAML==5.3.1
-Sphinx-Substitution-Extensions==2020.7.4.1
+Sphinx-Substitution-Extensions==2020.9.30.0
 Sphinx==3.2.1
 VWS-Test-Fixtures==2020.9.25.1
 attrs==20.2.0  # Modern attrs is required for pytest