Remove deprecation notice for sectionless nova_config

nova_config used to accept section-less configuration name.

This changed in the grizzly release of puppet-nova (c9757ec44)
and section name are now required.

This change removes the deprecation warning as enough time/releases
where givin for people to fix their manifests if section-less configs
were still in use.

Change-Id: I4c6e749fd48a8cf56df750feba6f7b94a7e43c8e
Merge "Remove deprecation notice for sectionless nova_config"