Remove 'All Rights Reserved' from the collection copyright and templates.

The original Berkeley Software Distributions were made in the 1980's
and 1990's. At that time, the Buenos Ares Convention of 1910 was in
force in most of the countries in the Americas. It required an
affirmative statement of rights reservation, typically using 'All
Rights Reserved.' The Regents included this phrase in their copyright
notices to invoke this treaty to ensure maximal copyright protection.

In the 1990's, Latin America coutries ratifeid the Berne Convention on
copyrights which prohibited them from requiring an affirmative
statement to reserve the rights. When Nicaragua ratified in 2000, the
Buenos Ares Convention of 1910 was effectively repealed. This made all
the 'All Rights Reserved' phrases obsolete and legal deadweight most
of the time, and certainly in the cases removed here.

Since it's no longer required, and is in fact meaningless, core has
decided to dropped it from the project's collection copyright and
sample templates. It encourages other rights holders to do the same
after consultation with their legal department.

More see https://en.wikipedia.org/wiki/Buenos_Aires_Convention for
more information.

Approved by: core@ (emaste@, jhb@)
Differential Review: https://reviews.freebsd.org/D15264