DOC: Update the Gitlab banner to new VTK logo design.

Thanks to Steve Jordan, the VTK new logos are now available at:
https://www.vtk.org/download/

This allows to:
- Update the Gitlab banner to new VTK logo design.
- Update the `vtkLogo.ico` icon resource.
- Remove the `vtkLogo.jpg` file to avoid duplicating data, since the
file is available at the above web site.

Resolves #17315