Moving all the minor versions after voltha-2.5

This is done to leave the bugfix versions available on the release
support branch

Change-Id: Ia3d32c869461414fcda91648878aa212536448b6
diff --git a/voltha/Chart.yaml b/voltha/Chart.yaml
index a786a97..ee6c38d 100644
--- a/voltha/Chart.yaml
+++ b/voltha/Chart.yaml
@@ -14,7 +14,7 @@
 ---
 apiVersion: "v1"
 name: "voltha"
-version: "2.6.1"
+version: "2.7.0-dev"
 description: "A Helm chart for Voltha based on K8S resources in Voltha project"
 keywords:
   - "onf"