Log Message:
Remove vtk-data 4.2

Recent vtk-data is no longer a set of static data files, but rather a
cmake ExternalData module. Quoting from cmake:

  Use this module to unambiguously reference data files stored
  outside the source tree and fetch them at build time from arbitrary
  local and remote content-addressed locations.

This is not in the spirit of pkgsrc, and users of VTKData would be expected
to unpack it in their local source tree anyway.