only run the jvb service on the additional jvb host

roles/matrix-jitsi/tasks/init_additional_jvb.yml

@@ -1,5 +1,5 @@
 ---
 
 - ansible.builtin.set_fact:
-    matrix_systemd_services_list: "{{ matrix_systemd_services_list + ['matrix-jitsi-jvb.service'] }}"
+    matrix_systemd_services_list: "{{ ['matrix-jitsi-jvb.service'] }}"
   when: matrix_jitsi_enabled | bool