monitoring: fix exporter service monitor selector

Exporter service created by rook operator contains the following labels:
`app=rook-ceph-exporter,rook_cluster=<cluster-name>`

Label `ceph_daemon_id=exporter` is not there and therefore the service
monitor selector can not discover the exporter service.

This fix removes the `ceph_daemon_id=exporter` label from the exporter
service monitor selector.

Signed-off-by: Matej Feder <matej.feder@dnation.cloud>
(cherry picked from commit 7053e761da)

deploy/examples/monitoring/exporter-service-monitor.yaml

@@ -13,7 +13,6 @@ spec:
     matchLabels:
       app: rook-ceph-exporter
       rook_cluster: rook-ceph # namespace:cluster
-      ceph_daemon_id: exporter
   endpoints:
     - port: ceph-exporter-http-metrics
       path: /metrics