chore(deps-dev): bump furo from 2021.9.8 to 2021.9.22

Bumps [furo](/~https://github.com/pradyunsg/furo) from 2021.9.8 to 2021.9.22.
- [Release notes](/~https://github.com/pradyunsg/furo/releases)
- [Changelog](/~https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2021.09.08...2021.09.22)

---
updated-dependencies:
- dependency-name: furo
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -67,7 +67,7 @@ black = "^20.8b1"
 flake8-black = "^0.2.3"
 safety = "^1.10.3"
 Sphinx = "^4.2.0"
-furo = "^2021.9.8"
+furo = "^2021.9.22"
 sphinx-argparse = "^0.3.1"
 coverage = {version = "^5.5", extras = ["toml"]}
 pygments = "^2.10.0"