Switch sphinx language to en
Switch sphinx language to en

With sphinx release of 5.0.0, they changed default for language variable
to 'en' from None. With that current None valuable is not valid and should
not be used.


Change-Id: I40b2635eafe8221218010d1c3cd5cf5717bc2800
openstack/openstack-ansible-memcached_server,openstack/openstack-ansible-memcached_server