[api-ref] Remove temporary block in conf.py
[api-ref] Remove temporary block in conf.py

The os-api-ref 1.0.0 is out. We can remove the support to older version now.
Reference:
https://github.com/openstack/senlin/commit/6d41feb58dd836d426c9b6f025846dbbf7295097

Change-Id: I1946a4c3cf51001b3c759008ce9c7da2ab646ee4

openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar