Make maubot communicate with the homeserver via the container network

Supersedes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2791

roles/custom/matrix-bot-maubot/templates/config/config.yaml.j2

@@ -60,7 +60,7 @@ server:
 homeservers:
   {{  matrix_domain }}:
     # Client-server API URL
-        url: "https://{{ matrix_server_fqn_matrix }}"
+        url: {{ matrix_homeserver_container_url | to_json }}
     # registration_shared_secret from synapse config
     # You can leave this empty if you don't have access to the homeserver.
     # When this is empty, `mbc auth --register` won't work, but `mbc auth` (login) will.