chore(deps-dev): bump sphinx from 3.0.3 to 3.0.4 (#322)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.0.3 to 3.0.4.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v3.0.3...v3.0.4)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>