doc: remove a insignificant line from go1.2.txt
doc: remove a insignificant line from go1.2.txt

Not a user-visible API change.  Just a minor garbage
win in contrived cases.

Also, the package is io/ioutil.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/12987044

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang