Build ref-protection plugin for Gerrit v3.2

Change-Id: I1456e63e135ff850f4ff557d3071c403a8ffcb2c
diff --git a/jenkins/gerrit-bazel-plugin-ref-protection.yaml b/jenkins/gerrit-bazel-plugin-ref-protection.yaml
index 0253a4d..6865053 100644
--- a/jenkins/gerrit-bazel-plugin-ref-protection.yaml
+++ b/jenkins/gerrit-bazel-plugin-ref-protection.yaml
@@ -6,6 +6,7 @@
             - master
           gerrit-branch:
             - master
+            - stable-3.2
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - stable-3.1