[VOL-2875] Update voltctl docs

(Cherry pick of https://gerrit.opencord.org/c/18460/)

Change-Id: I0f12410131f35533a473a5c52fc649e307802853
diff --git a/.gitreview b/.gitreview
index dba8a92..43c7604 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=voltctl.git
 defaultremote=origin
+defaultbranch=voltha-2.3