We don't need them any more since #15837 was fixed.

Fixes #19718

Change-Id: I13e46c62b321b2c9265f44c977b63bfb23163ca2
Reviewed-on: https://go-review.googlesource.com/38664
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>