[docs] [issue28785] Clarify the behavior of __eq__() returning NotImplemented

Changes by Martin Panter <vadmium+py@gmail.com>: ---------- title: Clarify the behavior of NotImplemented -> Clarify the behavior of __eq__() returning NotImplemented _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue28785> _______________________________________