Use random state 42 instead of 123

[nguyenmp]

As mentioned in the scipy tutorial, the speaker asked hte audience to make a pull request to change random state from 123 to 42 because it is a better number.

[bondarevts]

It will break the description for the exercise and the solution:

Print the true labels of 3 wrong predictions

[amueller]

good poing @bondarevts :) maybe not worth the hassle of fixing everything.