Remove portsnap(8)
Rather than having a tool in the FreeBSD base system for obtaining
the FreeBSD ports tree, users are encouraged to pkg install git
and then git clone https://git.FreeBSD.org/ports.git /usr/ports.
The portsnap servers will continue operating until FreeBSD 13 reaches
its End-of-Life, and portsnap is available from the ports tree as
ports-mgmt/portsnap.
Requested by: portmgr
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D39563
X-MFC: no