ps.1: Fix broken comment line

While here, remove the long-unused dash in the first line.

Reviewed by: ziaee, olce
Fixes: ddf144a04b53 ("ps.1: Revamp: Explain general principles, update to match reality")
MFC after: 1 day
Differential Revision: https://reviews.freebsd.org/D58038

(cherry picked from commit 759ce9a2b38e1de70c14c81dee7e245bf0bc6b94)