They are no longer needed by stkcheck.

Fixes #16057

Change-Id: I57cb55de5b7a7a1d31a3da200a3a2d51576b68f5
Reviewed-on: https://go-review.googlesource.com/26667
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>