Moving onos chart to latest again after release of voltha-onos with 2.2-latest

This reverts commit eba883990eeca6eeebb2d8bee6ee69cab5225e3b.

Reason for revert: <INSERT REASONING HERE>

Change-Id: Ic1ce79dff636dc0329c37fe0edffb15f2c48cfbc
diff --git a/voltha b/voltha
index 6acf458..52a45bf 100755
--- a/voltha
+++ b/voltha
@@ -127,7 +127,7 @@
 ONOS_CHART=${ONOS_CHART:-onf/onos}
 ONOS_CHART_VERSION=${ONOS_CHART_VERSION:-latest}
 ONOS_CLASSIC_CHART=${ONOS_CLASSIC_CHART:-onos/onos-classic}
-ONOS_CLASSIC_CHART_VERSION=${ONOS_CLASSIC_CHART_VERSION:-0.1.5}
+ONOS_CLASSIC_CHART_VERSION=${ONOS_CLASSIC_CHART_VERSION:-latest}
 KAFKA_CHART=${KAFKA_CHART:-incubator/kafka}
 KAFKA_CHART_VERSION=${KAFKA_CHART_VERSION:=latest}
 BBSIM_SADIS_SERVER_CHART=${BBSIM_SADIS_SERVER_CHART:-bbsim-sadis/bbsim-sadis-server}