mail/mailman3 update and change maintainer

From: Einar_Bjarni_Halldórsson <einar_at_isnic.is>
Date: Wed, 07 Dec 2022 15:20:17 UTC
Hi,

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=267890

Current maintainer has OK'd me taking over. As-is the port is completely 
broken. This patch syncs it with upstream and I've confirmed it builds 
and runs with current tree.

.einar