TEST-FIX: fixing vtkRenderingVolumePython-volTM3DCropRegions

This test added an observer which was not present in vtk and not required.

Change-Id: I5803475ceccaba1c066c188f30b1650619170321

Rendering/Volume/Testing/Python/volTM3DCropRegions.py

@@ -89,6 +89,5 @@ def TkCheckAbort (__vtk__temp0=0,__vtk__temp1=0):
         renWin.SetAbortRender(1)
         pass
 
-renWin.AddObserver(AbortCheckEvent,TkCheckAbort)
 iren.Initialize()
 # --- end of script --