doc: shorten project dashboard link
doc: shorten project dashboard link

Fixes issue 3420.
(which was already fixed)

R=golang-dev, bradfitz, dsymonds
CC=golang-dev
http://codereview.appspot.com/5987043
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go