runtime: remove comment that leaked into CL 153710043
runtime: remove comment that leaked into CL 153710043

This doesn't actually do anything. Maybe it will some day,
but maybe not.

TBR=r
CC=golang-codereviews
https://codereview.appspot.com/155490043

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