build(deps-dev): bump furo from 2023.3.27 to 2023.5.20 (#60)

Bumps [furo](https://github.com/pradyunsg/furo) from 2023.3.27 to 2023.5.20.
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2023.03.27...2023.05.20)

---
updated-dependencies:
- dependency-name: furo
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -4,4 +4,4 @@ sphinx-jinja2-compat>=0.1.1
 sphinx-toolbox>=2.16.0
 enum_tools==0.9.0.post1
 
-furo==2023.3.27
+furo==2023.5.20