Using correct ETCD chart version for VOLTHA-2.7

Change-Id: Ie2e5e9c56be435883f63785639a160f8f36987ac
diff --git a/releases/voltha-2.7 b/releases/voltha-2.7
index 5251c57..dbf119a 100644
--- a/releases/voltha-2.7
+++ b/releases/voltha-2.7
@@ -14,6 +14,7 @@
 export WITH_ONOS=classic
 export HELM_VERSION=v3.2.4
 export KIND_VERSION=v0.8.1
+export ETCD_CHART_VERSION=5.6.2
 
 # global.image_tag=null will use the image tags in the Helm charts rather than
 # kind-voltha's default which is 'master'.