misc/ios: don't refer to iostest.bash

iostest.bash might not live much longer, and all.bash is much
less confusing and more explicit.

Change-Id: If42e8716bbbb02aa3f817dceaabb1aa8076aae1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/175178


Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>