Build serviceuser plugin on its own stable-3.2 branch

Change-Id: I65c61c0735d2285741161bb23645bc6009f9fb20
diff --git a/jenkins/gerrit-bazel-plugin-serviceuser.yaml b/jenkins/gerrit-bazel-plugin-serviceuser.yaml
index c7a55ea..d28df39 100644
--- a/jenkins/gerrit-bazel-plugin-serviceuser.yaml
+++ b/jenkins/gerrit-bazel-plugin-serviceuser.yaml
@@ -6,9 +6,9 @@
             - master
           gerrit-branch:
             - master
-            - stable-3.2
       - 'plugin-{name}-bazel-{branch}':
           branch:
+            - stable-3.2
             - stable-3.1
             - stable-3.0
             - stable-2.16