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

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

Author: dependabot[bot]

pyproject.toml

@@ -241,7 +241,7 @@ dev = [
     "doc8==1.1.1",
     "dodgy==0.2.1",
     "freezegun==1.2.2",
-    "furo==2023.3.27",
+    "furo==2023.5.20",
     "mypy==1.3.0",
     "pdm==2.6.1",
     "pip_check_reqs==2.4.4",