CC-BY-3.0 was shiny and new back in 2009, but CC-BY-4.0 is
generally preferred now. Update our CC-BY uses to CC-BY-4.0.
Not sure how we ended up with both /doc/copyright and /copyright,
but redirect /doc/copyright to /copyright.
Google lawyers signed off on the overall CC-BY-4.0 update
and Renee French signed off on the update of the gopher license.
Change-Id: Ica8f6d51775623eb38ac0a9cba18dbc0a82faea4
Reviewed-on: https://go-review.googlesource.com/c/website/+/447156
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Russ Cox