Use voltha-rw-core v2.3.6

Change-Id: I13d42852039f7443686b295bc302552575881a0c
diff --git a/voltha/Chart.yaml b/voltha/Chart.yaml
index 925165c..dd168d0 100644
--- a/voltha/Chart.yaml
+++ b/voltha/Chart.yaml
@@ -17,7 +17,7 @@
 description: A Helm chart for Voltha based on K8S resources in Voltha project
 icon: https://guide.opencord.org/logos/cord.svg
 
-version: 2.3.0
+version: 2.3.1
 
 # app version applies to multiple components with potentially different
 # container image versions