Build automerger against gerrit stable-3.6

Bug: Issue 15831
Change-Id: I9d29786189ab425f01387b8351bf5c40403ea765
diff --git a/jenkins/gerrit-bazel-plugin-automerger.yaml b/jenkins/gerrit-bazel-plugin-automerger.yaml
index 840bb24..c826d93 100644
--- a/jenkins/gerrit-bazel-plugin-automerger.yaml
+++ b/jenkins/gerrit-bazel-plugin-automerger.yaml
@@ -6,6 +6,7 @@
             - master
           gerrit-branch:
             - master
+            - stable-3.6
             - stable-3.5
             - stable-3.4
             - stable-3.3