Add an empty value for cloud provider (#1869)

https://trello.com/c/oAjKlzc1/522-improvement-update-documentation-example-for-k8s-on-premises-backup

Author: renetapopova

modules/ROOT/pages/kubernetes/operations/backup-restore.adoc

@@ -353,7 +353,7 @@ backup:
   bucketName: "my-bucket"
   databaseAdminServiceName:  "standalone-admin"
   database: "neo4j,system"
-  cloudProvider:
+  cloudProvider: ""
 
 consistencyCheck:
   enabled: true