build: bump vtk from 9.3.1 to 9.4.1

Bumps [vtk](https://vtk.org) from 9.3.1 to 9.4.1.

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

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -68,7 +68,7 @@ tests = [
     "scipy==1.14.1",
     "semver==3.0.2",
     "six==1.17.0",
-    "vtk==9.3.1",
+    "vtk==9.4.1",
 ]
 tests-minimal = [
     "pytest==8.3.4",
@@ -106,7 +106,7 @@ doc = [
     "sphinx-copybutton==0.5.2",
     "sphinx-jinja==2.0.2",
     "trame-vtk==2.8.12",
-    "vtk==9.3.1",
+    "vtk==9.4.1",
 ]
 
 [project.urls]