Merge pull request #1184 from andyzhangx/fix-cloning-doc

doc: fix volume cloning doc

Author: andyzhangx

deploy/example/cloning/README.md

@@ -2,6 +2,10 @@
 ## Feature Status: Beta
 
 - supported from v1.23.2
+- NFSv3 protocol is not supported
+
+## Prerequisites
+- ensure that the virtual network on which the driver controller pod is running is included in the allowed list of the storage account VNet setting.
 
 ## Create a Source PVC