Restore missing wiring between matrix_dendrite_container_extra_arguments_auto and matrix_homeserver_container_extra_arguments_auto

I believe this wiring had gotten lost at some point before.

Fixes #3199

Author: spantaleev

group_vars/matrix_servers

@@ -4975,6 +4975,7 @@ matrix_dendrite_systemd_wanted_services_list_auto: |
     (['matrix-coturn.service'] if matrix_coturn_enabled else [])
   }}
 
+matrix_dendrite_container_extra_arguments_auto: "{{ matrix_homeserver_container_extra_arguments_auto }}"
 matrix_dendrite_app_service_config_files_auto: "{{ matrix_homeserver_app_service_config_files_auto }}"
 
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