It was already marked flaky for everything but the dashboard.
Remove that restriction. It's just flaky overall.

It's doing more harm than good.

Updates #13324

Change-Id: I36feff32a1b8681e77700f74b9c70cb4073268eb
Reviewed-on: https://go-review.googlesource.com/38459
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>