[MacPorts] #66975: qt6: Update to 6.4 (was: Update qt6 to 6.4)

[MacPorts]

#66975: qt6: Update to 6.4
--------------------------+--------------------
  Reporter:  MaddTheSane  |      Owner:  (none)
      Type:  update       |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:  2.8.1
Resolution:               |   Keywords:
      Port:  qt6          |
--------------------------+--------------------

Comment (by ryandesign):

 The port has no maintainer so you or someone will need to volunteer to do
 the update.

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Ticket URL: <https://trac.macports.org/ticket/66975#comment:1>
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