Update events-gcloud-pubsub build

stable-3.4 builds against gerrit stable-3.4
stable-3.5 builds against gerrit stable-3.5
master builds against gerrit stable-3.6

Change-Id: I4b1efcf894493b7dc91d4150b2c3c00117f8b918
diff --git a/jenkins/gerrit-bazel-plugin-events-gcloud-pubsub.yaml b/jenkins/gerrit-bazel-plugin-events-gcloud-pubsub.yaml
index 21290c4..a15e827 100644
--- a/jenkins/gerrit-bazel-plugin-events-gcloud-pubsub.yaml
+++ b/jenkins/gerrit-bazel-plugin-events-gcloud-pubsub.yaml
@@ -5,9 +5,10 @@
           branch:
             - master
           gerrit-branch:
-            - stable-3.5
-            - stable-3.4
+            - stable-3.6
       - 'plugin-{name}-bazel-{branch}':
           branch:
+            - stable-3.5
+            - stable-3.4
             - stable-3.3
       - 'plugin-{name}-verifier'