Nothing uses it any more.

Change-Id: I42ee7222b06b1a79b8b44894f3071752f9166d7a
Reviewed-on: https://go-review.googlesource.com/14193
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>