pip install is missing vtkmodules for CadQuery 2.6.0

I installed `pip install --upgrade cadquery` in order to get version 2.6.0, but when I try to use it for some models, it no longer works as some dependencies seem to be missing:
```
File "D:\Programs\venv\Lib\site-packages\cadquery\occ_impl\shapes.py", line 23, in
from vtkmodules.vtkCommonDataModel import vtkPolyData
ModuleNotFoundError: No module named 'vtkmodules.vtkCommonDataModel'
```

I had to manually install `cadquery-vtk` in order to satisfy the requirement.
(This wasn't the case in earlier versions.)

I see that #1786 added some dependencies like `trame-vtk` to `setup.py`, just no `cadquery-vtk`.