Bump furo from 2023.3.27 to 2023.5.20

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:development
  update-type: version-update:semver-minor
...

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

setup.py

@@ -29,7 +29,7 @@
     "docs": [
         "Sphinx==7.0.1",
         "sphinx-issues==3.0.1",
-        "furo==2023.3.27",
+        "furo==2023.5.20",
     ]
     + FRAMEWORKS,
 }