Bump sphinx from 2.3.0 to 2.3.1
Bump sphinx from 2.3.0 to 2.3.1

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 2.3.0 to 2.3.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](https://github.com/sphinx-doc/sphinx/compare/v2.3.0...v2.3.1)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
aio-libs/aiohttp_security