secure/precis: Use internal/testtext runner

Change-Id: I73658f436dda909986b6a847c54945ec91a39744
Reviewed-on: https://go-review.googlesource.com/30253
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
4 files changed