runtime: fix typos
runtime: fix typos

LGTM=dvyukov
R=dvyukov
CC=golang-codereviews
https://codereview.appspot.com/141000043

tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go