Bump furo and black (#2385)

Updates `furo` from 2024.7.18 to 2024.8.6
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](https://github.com/pradyunsg/furo/compare/2024.07.18...2024.08.06)

Updates `black` from 24.4.2 to 24.8.0
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](https://github.com/psf/black/compare/24.4.2...24.8.0)

---
updated-dependencies:

  dependency-group: python-packages
- dependency-name: furo
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: python-packages
- dependency-name: black
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: python-packages
...

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

* Pin Sphinx==7.4.7

---------

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