FIX: Fix vtkAddon kit import

- vtkAddon is now part of vtkmodules and should be imported from it

Author: Thibault-Pelletier

Base/Python/vtkAddon.py

@@ -2,12 +2,4 @@
 namespace.
 """
 
-# Importing VTK is required for loading its Python modules and ensuring seamless instantiation
-# of VTK-based MRML or Slicer Python modules from code executed in both "PythonSlicer executable"
-# and the "Slicer Python Console" environments. For more details, see Base/Python/slicer/__init__.py
-import vtk  # noqa: F401
-
-from vtkAddonPython import *
-
-# Cleanup: Removing things the user shouldn't have to see.
-del vtk
+from vtkmodules.vtkAddonPython import *