Try to make Dimension wait for Synapse

Some people have reported Dimension failing to contact
matrix-nginx-proxy/Synapse on startup. This attempts to
delay Dimension startup some more.

group_vars/matrix_servers

@@ -912,6 +912,8 @@ matrix_dimension_systemd_required_services_list: |
     +
     (['matrix-postgres.service'] if matrix_postgres_enabled else [])
     +
+    (['matrix-synapse.service'] if matrix_synapse_enabled else [])
+    +
     (['matrix-nginx-proxy.service'] if matrix_nginx_proxy_enabled else [])
   }}