go.tools/importer: update comment (and absolve gri of blame) for non-bug.
go.tools/importer: update comment (and absolve gri of blame) for non-bug.

R=gri
CC=golang-dev
https://codereview.appspot.com/10911044

tmc/mirror-go.tools,tmc/mirror-go.tools,t-yuki/go.tools.old,t-yuki/go.tools.old,t-yuki/go.tools.old,tmc/mirror-go.tools