[MacPorts] #63069: vtk: migrate from python variants to subports

[MacPorts]

#63069: vtk: migrate from python variants to subports
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  Reporter:  mascguy  |      Owner:  mascguy
      Type:  defect   |     Status:  assigned
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:
      Port:  vtk      |
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Comment (by mascguy):

 It eliminates the need to use anything related to
 `require_active_variants`.

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Ticket URL: <https://trac.macports.org/ticket/63069#comment:2>
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