Dump admins to the auth-server users file without templating

We were omitting fields like u2f_registrations that were added after
this template was initially written. This syntax makes it easier to
keep things in sync.

roles/auth-server/templates/users.yml.j2

 ---
 
-{% for user in admins %}
-- name: "{{ user.name }}"
-  email: "{{ user.email }}"
-  password: "{{ user.password }}"
-  totp_secret: "{{ user.get('totp_secret', '') }}"
-  groups:
-    - admins
-{% endfor %}
+{#
+   This will include data we don't need (like ssh keys), but it's simple
+   and the auth-server will just ignore the extra data.
+#}
+{{ admins | to_nice_yaml }}