build(deps): bump pyvista from 0.43.5 to 0.43.6 in /requirements

Bumps [pyvista](https://github.com/pyvista/pyvista) from 0.43.5 to 0.43.6.
- [Release notes](https://github.com/pyvista/pyvista/releases)
- [Commits](pyvista/pyvista@v0.43.5...v0.43.6)

---
updated-dependencies:
- dependency-name: pyvista
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

requirements/requirements_doc.txt

@@ -4,7 +4,7 @@ imageio==2.34.1
 nest-asyncio==1.6.0
 notfound==1.0.2
 pypandoc==1.13
-pyvista==0.43.5
+pyvista==0.43.6
 sphinx-copybutton==0.5.2
 sphinx-gallery==0.15.0
 sphinx-notfound-page==1.0.0