Fixing chart version for openonu adapter

Change-Id: Ifda2190dbd637af05bf9c06f9dc596404b83a718
diff --git a/releases/voltha-2.6 b/releases/voltha-2.6
index 99aa2d2..3ab057c 100644
--- a/releases/voltha-2.6
+++ b/releases/voltha-2.6
@@ -6,7 +6,7 @@
 export VOLTHA_CHART_VERSION=2.7.2
 export VOLTHA_BBSIM_CHART_VERSION=4.1.5
 export VOLTHA_ADAPTER_OPEN_OLT_CHART_VERSION=2.7.1
-export VOLTHA_ADAPTER_OPEN_ONU_CHART_VERSION=2.7.0
+export VOLTHA_ADAPTER_OPEN_ONU_CHART_VERSION=2.6.8
 export ONOS_CLASSIC_CHART_VERSION=0.1.11
 export RADIUS_CHART_VERSION=1.0.2
 export VOLTCTL_VERSION=1.3.1