[docs] [issue16011] "in" should be consistent with return value of __contains__

Changes by Berker Peksag <berker.peksag@gmail.com>: ---------- nosy: +berker.peksag stage: needs patch -> patch review versions: +Python 3.5, Python 3.6, Python 3.7 -Python 3.2, Python 3.3, Python 3.4 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue16011> _______________________________________