math: remove repeated comment.
math: remove repeated comment.

R=golang-dev, nigeltao
CC=golang-dev
https://codereview.appspot.com/7835046

Committer: Nigel Tao <58ae08b3356928ff9c67562b4719487d54fe8348@golang.org>

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