COMP: Update usage of WRAP_EXCLUDE for Python

VTK has changed semantics of WRAP_EXCLUDE so that files with that property are
no longer ignored by Python wrapping. To explicitly exclude files from Python
wrapping, it's now necessary to set WRAP_EXCLUDE_PYTHON.

This fixes a build error like the following:

'/path/to/Slicer/Modules/Loadable/VolumeRendering/VolumeRenderingReplacements/VolumeRenderingReplacementsObjectFactory.h',
needed by 'Modules/Loadable/VolumeRendering/VolumeRenderingReplacements/VolumeRenderingReplacementsObjectFactoryPython.cxx',
missing and no known rule to make it

See https://github.com/Kitware/VTK/commit/e6f75b9.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25222 3bd1e089-480b-0410-8dfb-8563597acbee