COMP: Fix MSVC error C2516: 'ConstIterator': is not a legal base class

Originally reported by Astha, March 14, 2022, and further discussed at
"ITK build Error in itk::ShapedNeighborhoodIterator",
https://discourse.itk.org/t/itk-build-error-in-itk-shapedneighborhooditerator/4861

Modules/Core/Common/include/itkShapedNeighborhoodIterator.h

@@ -179,7 +179,7 @@ class ITK_TEMPLATE_EXPORT ShapedNeighborhoodIterator
   using typename Superclass::IndexValueType;
 
   /** An  iterator for the ShapedNeighborhood classes. */
-  struct Iterator : public ConstIterator
+  struct Iterator : public Superclass::ConstIterator
   {
     Iterator() = default;
     Iterator(Self * s)