Build zuul-results-summary plugin on stable-3.4 branch

Change-Id: Ia4104bb562492fc4d7b1e769b0d4fc56f91760dd
diff --git a/jenkins/gerrit-bazel-plugin-zuul-results-summary.yaml b/jenkins/gerrit-bazel-plugin-zuul-results-summary.yaml
index 69c201d..23403a0 100644
--- a/jenkins/gerrit-bazel-plugin-zuul-results-summary.yaml
+++ b/jenkins/gerrit-bazel-plugin-zuul-results-summary.yaml
@@ -6,4 +6,5 @@
             - main
           gerrit-branch:
             - master
+            - stable-3.4
             - stable-3.3