Build checks against gerrit stable-3.6

Bug: Issue 15831
Change-Id: If815529929d8ec3cc0a1512ca48fa83bdc318172
diff --git a/jenkins/gerrit-bazel-plugin-checks.yaml b/jenkins/gerrit-bazel-plugin-checks.yaml
index a401ce4..1ecddef 100644
--- a/jenkins/gerrit-bazel-plugin-checks.yaml
+++ b/jenkins/gerrit-bazel-plugin-checks.yaml
@@ -11,3 +11,4 @@
           gerrit-branch:
             - stable-3.4
             - stable-3.5
+            - stable-3.6