Issue #25195: Fix a regression in mock.MagicMock

_Call is a subclass of tuple (changeset 3603bae63c13 only works
for classes) so we need to implement __ne__ ourselves.

Patch by Andrew Plummer.

diff --cc Lib/unittest/mock.py
Simple merge

diff --cc Lib/unittest/test/testmock/testmock.py
Simple merge

diff --cc Misc/NEWS
Simple merge