www/moinmoin: reassign to wiki-admin@.

Even though this port is old and depends on the deprecated python2,
we are still using it as wiki.FreeBSD.org. So, mark it as safe
from deprecation by anyone who does not know that.

There is an open task to either update the wiki (v3 is a complete
rewrite), or to migrate it to something never.

PR: 298009
Approved by: lwhsa (as python@)