Bump sphinx-substitution-extensions from 2020.2.21.0 to 2020.4.5.0
Bump sphinx-substitution-extensions from 2020.2.21.0 to 2020.4.5.0

Bumps [sphinx-substitution-extensions](https://github.com/adamtheturtle/sphinx-substitution-extensions) from 2020.2.21.0 to 2020.4.5.0.
- [Release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases)
- [Changelog](https://github.com/adamtheturtle/sphinx-substitution-extensions/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/adamtheturtle/sphinx-substitution-extensions/compare/2020.02.21.0...2020.04.05.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
adamtheturtle/vws-python,adamtheturtle/vws-python