Mark matrix_nginx_proxy_proxy_jitsi_additional_jvbs as deprecated

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2842

roles/custom/matrix-nginx-proxy/tasks/validate_config.yml

@@ -16,6 +16,7 @@
     - {'old': 'matrix_nginx_proxy_reload_cron_time_definition', 'new': '<not configurable anymore>'}
     - {'old': 'matrix_nginx_proxy_container_labels_traefik_proxy_matrix_rule', 'new': '<split into matrix_nginx_proxy_container_labels_traefik_proxy_matrix_client_rule and matrix_nginx_proxy_container_labels_traefik_proxy_matrix_federation_rule>'}
     - {'old': 'matrix_nginx_proxy_container_labels_traefik_proxy_matrix_hostname', 'new': '<split into matrix_nginx_proxy_container_labels_traefik_proxy_matrix_client_hostname and matrix_nginx_proxy_container_labels_traefik_proxy_matrix_federation_hostname>'}
+    - {'old': 'matrix_nginx_proxy_proxy_jitsi_additional_jvbs', 'new': '<auto-determined from the jitsi_jvb_servers group in inventory/hosts - see docs/configuring-playbook-jitsi.md>'}
 
 - name: Fail on unknown matrix_ssl_retrieval_method
   ansible.builtin.fail: