net/http/pprof: fix doc for /debug/pprof/ Fixes issue 4548.
net/http/pprof: fix doc for /debug/pprof/
Fixes issue 4548.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/6944053

firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old