build(deps): bump vtk from 9.3.0 to 9.3.1 in /requirements (#451)

Bumps [vtk](https://vtk.org) from 9.3.0 to 9.3.1.

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

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

requirements/requirements_doc.txt

@@ -9,4 +9,4 @@ sphinx-copybutton==0.5.2
 sphinx-gallery==0.16.0
 sphinx-notfound-page==1.0.2
 trame==3.6.3
-vtk==9.3.0
+vtk==9.3.1