[1.6.x] Fixed #24250 -- Corrected mistakes in FormMixin docs.
[1.6.x] Fixed #24250 -- Corrected mistakes in FormMixin docs.

Backport of 5d193d042a3cc49033f0e8b5125913650d779496 from master

felixjimenez/django,redhat-openstack/django,felixjimenez/django,django-nonrel/django,redhat-openstack/django,django-nonrel/django,felixjimenez/django,redhat-openstack/django,felixjimenez/django,django-nonrel/django,django-nonrel/django,redhat-openstack/django