Remove the unnecessary horizon_auth

the auth is used for registry, but the horizon not need, so the
openstack_horizon_auth should be remove.
refer to https://github.com/openstack/kolla-ansible/blob/master/ansible/roles/nova/tasks/register.yml#L13

Change-Id: Ibd8985651bd64cba3e30c15596f0ae6d692b973b

ansible/roles/horizon/defaults/main.yml

@@ -56,8 +56,6 @@ horizon_image_full: "{{ horizon_image }}:{{ horizon_tag }}"
 ####################
 # OpenStack
 ####################
-openstack_horizon_auth: "{'auth_url':'{{ openstack_auth.auth_url }}','username':'{{ openstack_auth.username }}','password':'{{ openstack_auth.password }}','project_name':'{{ openstack_auth.project_name }}'}"
-
 horizon_logging_debug: "{{ openstack_logging_debug }}"