Add it-storyboard build for stable-2.13 branch

Change-Id: I5fa455e2d44587e0537fc15489c4b81346680ae3
diff --git a/jenkins/gerrit-buck-plugin-its-storyboard.yaml b/jenkins/gerrit-buck-plugin-its-storyboard.yaml
index 8d50469..3f56131 100644
--- a/jenkins/gerrit-buck-plugin-its-storyboard.yaml
+++ b/jenkins/gerrit-buck-plugin-its-storyboard.yaml
@@ -3,6 +3,7 @@
     branch:
       - master
       - stable-2.11
+      - stable-2.13
     jobs:
       - 'plugin-its-{name}-{branch}'