Bump sphinx-toolbox from 3.8.3 to 3.9.0

Bumps [sphinx-toolbox](https://github.com/sphinx-toolbox/sphinx-toolbox) from 3.8.3 to 3.9.0.
- [Release notes](https://github.com/sphinx-toolbox/sphinx-toolbox/releases)
- [Changelog](https://github.com/sphinx-toolbox/sphinx-toolbox/blob/master/doc-source/changelog.rst)
- [Commits](sphinx-toolbox/sphinx-toolbox@v3.8.3...v3.9.0)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -54,7 +54,7 @@ docs = [
     "myst-nb==1.2.0",
     "sphinx-book-theme==1.1.4",
     "sphinx-argparse==0.5.2",
-    "sphinx-toolbox==3.8.3",
+    "sphinx-toolbox==3.9.0",
 ]
 
 [project.scripts]