Issue #21408: The default __ne__() now returns NotImplemented if __eq__()

returned NotImplemented.  Removed incorrect implementations of __ne__().

diff --cc Lib/_collections_abc.py
Simple merge

diff --cc Lib/doctest.py
Simple merge

diff --cc Lib/pathlib.py
Simple merge

diff --cc Misc/NEWS
Simple merge

diff --cc Objects/typeobject.c
Simple merge