doc: remove left and right padding in H2 headings.
doc: remove left and right padding in H2 headings.

R=adg, rsc1, rsc
CC=golang-dev
http://codereview.appspot.com/4491041

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go