ports-mgmt/portmaster: update to version 3.21

Merge pull request #47 by Oleg Pudeyev:

Do not delete distfiles by default.

Merge pull request #59 by Babak Farrokhi:

Add -U alias for --update-if-newer

Merge pull request #71 by Kubilay Kocak:

Update IRC Channel Link (libera chat)

Fix issue #68 opened by Helmut1972

Make --no-confirm affect display of package messages

Any package messages of updated ports are displayed at the end of the
port updates, normally through a pager requiring conformation of each
page displayed.

This update makes --cno-confirm remove the need to confirm the display
of package messages.