bridge tests: Remove unneeded 'All rights reserved.'

The FreeBSD foundation no longer requires this, as per
https://lists.freebsd.org/pipermail/svn-src-all/2019-February/177215.html and
private communications.

Sponsored by: The FreeBSD Foundation

(cherry picked from commit e3c73f3d74c77b2c168519b10bdb6910a84287ef)