chore(deps-dev): Bump sphinx-toolbox from 4.2.0rc1 to 4.2.0 (#3200)

Bumps [sphinx-toolbox](https://github.com/sphinx-toolbox/sphinx-toolbox) from 4.2.0rc1 to 4.2.0.
- [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@v4.2.0rc1...v4.2.0)

---
updated-dependencies:
- dependency-name: sphinx-toolbox
  dependency-version: 4.2.0
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

pyproject.toml

@@ -93,7 +93,7 @@ optional-dependencies.dev = [
     "sphinx-paramlinks==0.6",
     "sphinx-pyproject==0.3.0",
     "sphinx-substitution-extensions==2026.1.12",
-    "sphinx-toolbox==4.2.0rc1",
+    "sphinx-toolbox==4.2.0",
     "sphinxcontrib-httpdomain==2.0.0",
     "sphinxcontrib-spelling==8.0.2",
     # ``sphinxcontrib-towncrier`` renders unreleased news fragments