runtime: fix comment Void function can not return false.
runtime: fix comment
Void function can not return false.

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://codereview.appspot.com/52000043

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang