runtime: fix typo in comment
runtime: fix typo in comment

R=golang-dev, dvyukov
CC=golang-dev
http://codereview.appspot.com/5540059

Committer: Dmitriy Vyukov <05e8181be3150e47da8fe2e1f18d381c75496ff4@google.com>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go