Build oauth plugin on stable-3.4 branch

Change-Id: Icd0d04058e77cd22ef7aead6545483f692de9d15
diff --git a/jenkins/gerrit-bazel-plugin-oauth.yaml b/jenkins/gerrit-bazel-plugin-oauth.yaml
index 219442b..4c0736a 100644
--- a/jenkins/gerrit-bazel-plugin-oauth.yaml
+++ b/jenkins/gerrit-bazel-plugin-oauth.yaml
@@ -11,4 +11,5 @@
             - master
           gerrit-branch:
             - master
+            - stable-3.4
             - stable-3.3