prometheus: add target relay.fedi.buzz

hosts/prometheus/default.nix

@@ -88,6 +88,8 @@
           labels.__meta_net = "net-flpk";
         } {
           targets = [ "localhost:${toString config.services.prometheus.exporters.collectd.port}" ];
+        } {
+          targets = [ "relay.fedi.buzz" ];
         } ];
     }];