content/go-brand: make slide theme license match all our other content

The blog post says the slide theme is licensed under
Creative Commons Attribution-ShareAlike 4.0 International License
but we license all our blog content and the gopher images
under Creative Commons Attributions 3.0.
Do the same here, after discussion with Steve Francia.
The use of CC-SA 4 was an oversight.

Change-Id: I0bfa720627be719107636f483aca01ba94b229a4
Reviewed-on: https://go-review.googlesource.com/109916
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/content/go-brand.article b/content/go-brand.article
index f03a672..f1e0cbb 100644
--- a/content/go-brand.article
+++ b/content/go-brand.article
@@ -59,8 +59,9 @@
 slides as it is easy to share and maintain updates. People are welcome to port
 them to keynote, powerpoint, etc.
 
-The slide themes are licensed under a Creative Commons Attribution-ShareAlike
-4.0 International License. The photos in the slides are all from
+Like this blog and all our gopher images,
+the slide themes are Creative Commons Attribution 3.0 licensed.
+The photos in the slides are all from
 [[https://unsplash.com/][unsplash]] and are released under the unsplash license.
 
 Instructions to use slides:
diff --git a/content/gopher.article b/content/gopher.article
index d21e32f..a5d8ffd 100644
--- a/content/gopher.article
+++ b/content/gopher.article
@@ -50,7 +50,7 @@
 
 The Go gopher is a character; a unique creation. Not any old gopher, just as Snoopy is not any old cartoon dog.
 
-The [[https://golang.org/doc/gopher/][gopher images]] are Creative Commons Attributions 3.0 licensed. That means you can play with the images but you must give credit to their creator (Renee French) wherever they are used.
+The [[https://golang.org/doc/gopher/][gopher images]] are Creative Commons Attribution 3.0 licensed. That means you can play with the images but you must give credit to their creator (Renee French) wherever they are used.
 
 Here are a few gopher adaptations that people have used as mascots for user group mascots and similar organizations.