stand: Remove obsolete junk

We long ago changed newvers.sh to make these comments bogus. Remove
them since every single one of them is broken after the $FreeBSD$
removal.

MFC Note: veriexec loader not updates since not in 13

Sponsored by: Netflix
Reviewed by: kevans, jhb
Differential Revision: https://reviews.freebsd.org/D45879

(cherry picked from commit 8165650389ba2d0a68cea6902ac3750055cad9da)