Fix small error in README.rst
Fix small error in README.rst

Change-Id: Iba33df0c19d895be98e6f63467f6d3143fae88c0

openstack-infra/shade,dtroyer/python-openstacksdk,stackforge/python-openstacksdk,openstack/python-openstacksdk,jsmartin/shade,stackforge/python-openstacksdk,jsmartin/shade,dtroyer/python-openstacksdk,openstack/python-openstacksdk,openstack-infra/shade