Build stable-3.0 branch of quota plugin

Change-Id: I1ee2fc0ee42c4f63b454f0757808ed08755bbffe
diff --git a/jenkins/gerrit-bazel-plugin-quota.yaml b/jenkins/gerrit-bazel-plugin-quota.yaml
index d790896..0cc166d 100644
--- a/jenkins/gerrit-bazel-plugin-quota.yaml
+++ b/jenkins/gerrit-bazel-plugin-quota.yaml
@@ -4,4 +4,5 @@
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
+            - stable-3.0
             - stable-2.16