Deprecate grpc metrics in ceph-csi

As kubernetes CSI sidecar is exposing the
GRPC mertics we can make use of the same in
ceph-csi we dont need to expose our own.

update: #881

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

examples/service-monitor.yaml

@@ -20,6 +20,3 @@ spec:
     - port: http-metrics
       path: /metrics
       interval: 5s
-    - port: grpc-metrics
-      path: /metrics
-      interval: 5s