[1.6.x] Fixed #21306 -- Documented lower-casing behavior of title filter.
[1.6.x] Fixed #21306 -- Documented lower-casing behavior of title filter.

Backport of eafe279120 from master

redhat-openstack/django,felixjimenez/django,redhat-openstack/django,django-nonrel/django,redhat-openstack/django,redhat-openstack/django,dex4er/django,felixjimenez/django,dex4er/django,django-nonrel/django,django-nonrel/django,felixjimenez/django,felixjimenez/django,dex4er/django,django-nonrel/django