Merge pull request #1406 from marquiz/docs/metrics

docs: clarify nfd_node_update_requests_total metric

Author: k8s-ci-robot

docs/deployment/metrics.md

@@ -17,7 +17,7 @@ The exposed metrics are
 | ------------------------------------------------- | --------- | ---------------------------------------
 | `nfd_master_build_info`                           | Gauge     | Version from which nfd-master was built
 | `nfd_worker_build_info`                           | Gauge     | Version from which nfd-worker was built
-| `nfd_node_update_requests_total`                  | Counter   | Number of node update requests processed by the master
+| `nfd_node_update_requests_total`                  | Counter   | Number of node update requests received by the master over gRPC
 | `nfd_node_updates_total`                          | Counter   | Number of nodes updated
 | `nfd_node_update_failures_total`                  | Counter   | Number of nodes update failures
 | `nfd_node_labels_rejected_total`                  | Counter   | Number of nodes labels rejected by nfd-master