Correct pluarity of "Python SDKs"
Correct pluarity of "Python SDKs"

The titles and lead-in text make it sound like there is "one SDK" which
is not accurate. Rather, there is discussion of the various Python SDKs.

Change-Id: I923b54c43f581afb329e359cb38c59bf485e0183

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals