Updating tutorial assets to work with 1.13.1

Change-Id: Icfa6c0b9a35e869b68a7c1ff394144a3ba0256c4
diff --git a/tools/tutorials/vm/destroyCluster b/tools/tutorials/vm/destroyCluster
index 9bc3a74..1ef04e2 100755
--- a/tools/tutorials/vm/destroyCluster
+++ b/tools/tutorials/vm/destroyCluster
@@ -1,10 +1,6 @@
 #!/bin/bash
-# -----------------------------------------------------------------------------
-# Destroys the ONOS cluster by stopping the 3 docker containers.
-# -----------------------------------------------------------------------------
 
-# Creates ONOS cluster using ONOS docker images
-ONOS_IMAGE=onosproject/onos:1.12.0
+# Destroys ONOS cluster running as ONOS docker images
 SSH_KEY=$(cut -d\  -f2 ~/.ssh/id_rsa.pub)
 
 for i in {1..3}; do