Bump pyvista from 0.38.1 to 0.38.3 in /requirements (#216)

Bumps [pyvista](https://github.com/pyvista/pyvista) from 0.38.1 to 0.38.3.
- [Release notes](https://github.com/pyvista/pyvista/releases)
- [Commits](pyvista/pyvista@v0.38.1...v0.38.3)

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

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

Author: dependabot[bot]

requirements/requirements_docs.txt

@@ -2,7 +2,7 @@ Sphinx<6
 ansys-sphinx-theme==0.9.4
 notfound==1.0.2
 pypandoc==1.10
-pyvista==0.38.1
+pyvista==0.38.3
 sphinx-copybutton==0.5.1
 sphinx-gallery==0.11.1
 sphinx-notfound-page==0.8.3