[MacPorts] #69924: opencv3: update to 3.4.20

[MacPorts]

#69924: opencv3: update to 3.4.20
------------------------+------------------------------------
 Reporter:  mohd-akram  |      Owner:  (none)
     Type:  update      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:
 Keywords:              |       Port:  opencv3, opencv3-devel
------------------------+------------------------------------
 https://github.com/opencv/opencv/wiki/ChangeLog#version3420

-- 
Ticket URL: <https://trac.macports.org/ticket/69924>
MacPorts <https://www.macports.org/>
Ports system for macOS