MAINT: Bump the actions group across 1 directory with 2 updates

Bumps the actions group with 2 updates in the /requirements directory: [pyvista](https://github.com/pyvista/pyvista) and [sphinx](https://github.com/sphinx-doc/sphinx).


Updates `pyvista` from 0.43.10 to 0.44.0
- [Release notes](https://github.com/pyvista/pyvista/releases)
- [Commits](pyvista/pyvista@v0.43.10...v0.44.0)

Updates `sphinx` from 7.3.7 to 7.4.0
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v7.3.7...v7.4.0)

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

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

requirements/requirements_doc.txt

@@ -12,8 +12,8 @@ panel==1.4.4
 plotly==5.22.0
 pypandoc==1.13
 pythreejs==2.4.2
-pyvista==0.43.10
-Sphinx==7.3.7
+pyvista==0.44.0
+Sphinx==7.4.0
 sphinx-copybutton==0.5.2
 sphinx-gallery==0.16.0
 sphinx-autobuild==2024.4.16