Update docs

docs/content/logging-and-monitoring/prometheus.md

@@ -50,7 +50,7 @@ The Ingress Controller exports the following metrics:
   * `controller_ingress_resources_total`. Number of handled Ingress resources. This metric includes the label type, that groups the Ingress resources by their type (regular, [minion or master](/nginx-ingress-controller/configuration/ingress-resources/cross-namespace-configuration)). **Note**: The metric doesn't count minions without a master.
   * `controller_virtualserver_resources_total`. Number of handled VirtualServer resources.
   * `controller_virtualserverroute_resources_total`. Number of handled VirtualServerRoute resources. **Note**: The metric counts only VirtualServerRoutes that have a reference from a VirtualServer.
-  * `location_zone` (services) metrics:
+  * `location_zone` (upstream services) metrics:
     * `location_zone_sent`. Number of bytes sent to clients.
     * `location_zone_received`. Number of bytes received from clients.
     * `location_zone_requests`. Total number of client requests.