Bump sphinx from 8.0.2 to 8.1.3 (#380)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 8.0.2 to 8.1.3.
- [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@v8.0.2...v8.1.3)

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

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

requirements_docs.txt

@@ -19,7 +19,7 @@ pytest-sphinx==0.6.3
 pyvista-xarray==0.1.7
 pyvista[all]==0.44.1
 scipy==1.14.1
-Sphinx==8.0.2
+Sphinx==8.1.3
 sphinx-autobuild==2024.10.3
 sphinx-book-theme==1.1.3
 sphinx-copybutton==0.5.2