content: fix 7years typo

Change-Id: Ie5f89b8763f473d38e9dc83e0793a9e161aa546d
Reviewed-on: https://go-review.googlesource.com/33023
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
1 file changed