[MacPorts] #51310: ImageMagick: update to 7.x

[MacPorts]

#51310: ImageMagick: update to 7.x
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  Reporter:  mopihopi     |      Owner:  ryandesign
      Type:  update       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  ImageMagick  |
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Comment (by kencu):

 that is not a workflow we’ve used before (having an active fork that
 accepts PRs for a bigger project like this)… but I can see the logic there
 to doing that.

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Ticket URL: <https://trac.macports.org/ticket/51310#comment:70>
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