build(deps): bump sphinx-toolbox from 3.7.0 to 3.8.0 in /requirements

Bumps [sphinx-toolbox](https://github.com/sphinx-toolbox/sphinx-toolbox) from 3.7.0 to 3.8.0.
- [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@v3.7.0...v3.8.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements/requirements_doc.txt

@@ -1,7 +1,7 @@
 Sphinx==8.0.2
 ansys-sphinx-theme==1.0.3
 sphinx-copybutton==0.5.2
-sphinx_toolbox==3.7.0
+sphinx_toolbox==3.8.0
 sphinx_design==0.6.1
 sphinxcontrib-mermaid>=0.7.1
 sphinx-gallery==0.17.1