compress/flate: fix typo in comment.
compress/flate: fix typo in comment.

R=golang-dev, nigeltao_gnome, nigeltao
CC=golang-dev
http://codereview.appspot.com/3334041

Committer: Nigel Tao <58ae08b3356928ff9c67562b4719487d54fe8348@golang.org>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go