[MacPorts] #54832: update gentoo mirrors

[MacPorts]

#54832: update gentoo mirrors
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 Reporter:  mojca   |      Owner:
     Type:  defect  |     Status:  new
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:
 Keywords:          |       Port:
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 The gentoo mirrors from `_resources/port1.0/fetch/mirror_sites.tcl` seem
 pretty outdated. In particular `http://gentoo.in.th/distfiles/` doesn't
 seem to work but neither does the command to list the mirrors.

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Ticket URL: <https://trac.macports.org/ticket/54832>
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