Replace Mailman to Mlmmj addresses

[dbaio]

Summary

Following mailing lists migration from Mailman to Mlmmj.

A few things are pending to do later.

• Replace these variables {mailman-*}:

:mailman-lists-desc: FreeBSD list server
:mailman-lists-url: https://lists.freebsd.org
:mailman-lists: {mailman-lists-url}[{mailman-lists-des

with

:project-lists-desc: FreeBSD list server
:project-lists-url: https://lists.freebsd.org
:project-lists: {mailman-lists-url}[{mailman-lists-des

and

• articles/freebsd-questions: Change Subscribe and Unsubscribe sections

https://docs.freebsd.org/en/articles/freebsd-questions/