snc.sh: use oc adm prune renderedmachineconfigs to remove older mac…

…hine configs

snc.sh

@@ -263,9 +263,7 @@ wait_till_cluster_stable openshift-marketplace
 retry ${OC} delete pod --field-selector=status.phase==Succeeded --all-namespaces
 
 # Delete outdated rendered master/worker machineconfigs and just keep the latest one
-mc_name=$(retry ${OC} get mc --sort-by=.metadata.creationTimestamp --no-headers -oname)
-echo "${mc_name}" | grep rendered-master | head -n -1 | xargs -t ${OC} delete
-echo "${mc_name}" | grep rendered-worker | head -n -1 | xargs -t ${OC} delete
+${OC} adm prune renderedmachineconfigs --confirm
 # Wait till machine config pool is updated correctly
 while retry ${OC} get mcp master -ojsonpath='{.status.conditions[?(@.type!="Updated")].status}' | grep True; do
     echo "Machine config still in updating/degrading state"