ENH: Update VTK to include vtkPythonUtil tweak

This change prevents crashes observed while investigating the impact of
python module loading on the startup time.

Merge request has been submitted upstream.
See https://gitlab.kitware.com/vtk/vtk/merge_requests/1515

$ git shortlog fe92273..1c30cb0 --no-merges
Jean-Christophe Fillion-Robin (1):
BUG: vtkPythonUtil: Check if vtkPythonMap is valid

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25109 3bd1e089-480b-0410-8dfb-8563597acbee