build(deps): update dependency sphinx-toolbox to v3.8.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
sphinx-toolbox	==3.7.0 -> ==3.8.0

---

Release Notes

sphinx-toolbox/sphinx-toolbox (sphinx-toolbox)

### [`v3.8.0`](https://redirect.github.com/sphinx-toolbox/sphinx-toolbox/releases/tag/v3.8.0): Version 3.8.0 [Compare Source](https://redirect.github.com/sphinx-toolbox/sphinx-toolbox/compare/v3.7.0...v3.8.0) Automatically copied from [PyPI](https://pypi.org/project/sphinx-toolbox/3.8.0). *** Powered by OctoCheese\ [📝 docs](https://octocheese.readthedocs.io) | [:octocat: repo](https://redirect.github.com/domdfcoding/octocheese) | [🙋 issues](https://redirect.github.com/domdfcoding/octocheese/issues) | [🏪 marketplace](https://redirect.github.com/marketplace/octocheese)

---

Configuration

📅 Schedule: Branch creation - "every weekend" in timezone Etc/UTC, Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• [ ] If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.