Remove unnecessary lower constraints
Remove unnecessary lower constraints

This change removes unneeded lower constraints.

Change-Id: Ibefa12ddedae14a93e9ab914f62ce8247e0ee4ce
Signed-off-by: Nicolas Bock <4ad6fd604400c7892c7a2cb53bf674987bcaa405@canonical.com>

openstack/designate,openstack/designate,openstack/designate