Update vtk requirement from <9.6 to <9.7 (#630)

Updates the requirements on [vtk](https://vtk.org) to permit the latest version.

---
updated-dependencies:
- dependency-name: vtk
  dependency-version: 9.6.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

pyproject.toml

@@ -46,7 +46,7 @@ docs = [
   'typed-ast==1.5.5',
   'typing_extensions==4.15.0',
   'vtk-xref==0.1.1',
-  'vtk<9.6',
+  'vtk<9.7',
 ]
 
 [tool.ruff]