doc/code: update newmath.Sqrt test case to make sure test succeed         Fixes issue 3445.
doc/code: update newmath.Sqrt test case to make sure test succeed
        Fixes issue 3445.

R=golang-dev, rsc, mtj
CC=golang-dev
http://codereview.appspot.com/5975061
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go