staging: disable allocation of grafana on piranha

piranha does not seem to be available from the outside world currently

cluster/staging/app/telemetry/deploy/telemetry-service.hcl

@@ -79,6 +79,12 @@ job "telemetry-service" {
   group "grafana" {
     count = 1
 
+    constraint {
+      attribute = "${attr.unique.hostname}"
+      operator = "!="
+      value = "piranha"
+    }
+
     network {
       port "grafana" {
         static = 3719