Drop 'not in' and 'is not' tests from HACKING.rst
Drop 'not in' and 'is not' tests from HACKING.rst

These rules were removed from hacking in Ic01e55781d36328a03692418537b642f1f719d1b
Since they are now covered directly in pep8. HACKING.rst is a list of
rules that augment pep8, and should not restate any pep8 rules.

Change-Id: Idb8298f7ff8f09693e98f4ee8b5a25b0b13a5951

hyakuhei/cleantox,hyakuhei/cleantox,zancas/hacking,zancas/hacking,openstack-dev/hacking,openstack-dev/hacking