VOL-2379 Release voltha-openonu-adapter 2.2.6

Change-Id: Iccff81c3403e9fbec2089056e22b09d2cd7ef29b
diff --git a/VERSION b/VERSION
index f963933..bda8fbe 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.2.6-dev
+2.2.6