doc: remove cov and prof from /ref/cmd
doc: remove cov and prof from /ref/cmd

Update issue 3400

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/5921044

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