chore(deps-dev): update sphinx requirement

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/v8.1.3/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v5.1.1...v8.1.3)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 8.1.3
  dependency-type: direct:development
...

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

Author: dependabot[bot]

pyproject.toml

@@ -53,7 +53,7 @@ dev = [
     "cyclonedx-bom >=4.0.0,<5.0.0",
 ]
 docs = [
-    "sphinx >=5.1.1,<9.0.0",
+    "sphinx >=8.1.3,<9.0.0",
     "sphinx-markdown-builder >=0.6.4,<1.0.0",
 ]
 hooks = [