Update .gitreview to stable/vanadium

Change-Id: I7c238bf617d4a701aba5bb8a17e3e7da3199576b
Signed-off-by: jenkins-releng <[email protected]>

Author: jenkins-releng

.gitreview

@@ -2,4 +2,4 @@
 host=git.opendaylight.org
 port=29418
 project=ovsdb.git
-defaultbranch=master
+defaultbranch=stable/vanadium