doc: update effective_go.tmpl
doc: update effective_go.tmpl

Forgot this half in http://codereview.appspot.com/5764044

R=gri
CC=golang-dev
http://codereview.appspot.com/5770044

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang