Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

unifdef: Fix case where a multiline comment follows a directive.

Sponsored by: Klara, Inc.
Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D41026

Link in NetBSD's unifdef(1) tests

Skip one, is it currently fails.