[MacPorts] #44804: Update protobuf-cpp to 2.6.0

[MacPorts]

#44804: Update protobuf-cpp to 2.6.0
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 Reporter:  nomis52@…  |      Owner:  macports-tickets@…
     Type:  update     |     Status:  new
 Priority:  Normal     |  Milestone:
Component:  ports      |    Version:  2.3.1
 Keywords:             |       Port:  protobuf-cpp
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 A new version of protobuf has been released.

 Also note the homepage has moved to github:
 https://github.com/google/protobuf

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Ticket URL: <https://trac.macports.org/ticket/44804>
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