Bump furo from 2023.5.20 to 2023.8.19

Bumps [furo](https://github.com/pradyunsg/furo) from 2023.5.20 to 2023.8.19.
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2023.05.20...2023.08.19)

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

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

requirements/docs.txt

@@ -1,6 +1,6 @@
 -r main.txt
 enum-tools[sphinx]==0.10.0
-furo==2023.5.20
+furo==2023.8.19
 Sphinx>4,<8
 sphinx-autobuild==2021.3.14
 sphinx-copybutton==0.5.2