Build serviceuser against gerrit stable-3.6

Bug: Issue 15831
Change-Id: I008d81ce2800bee12d2acbe9f45d1eb55c56bfaa
diff --git a/jenkins/gerrit-bazel-plugin-serviceuser.yaml b/jenkins/gerrit-bazel-plugin-serviceuser.yaml
index 426e038..8784c06 100644
--- a/jenkins/gerrit-bazel-plugin-serviceuser.yaml
+++ b/jenkins/gerrit-bazel-plugin-serviceuser.yaml
@@ -6,6 +6,7 @@
             - master
           gerrit-branch:
             - master
+            - stable-3.6
             - stable-3.5
             - stable-3.4
       - 'plugin-{name}-bazel-{branch}':