Build the project-group-structure plugin on stable-2.16

Change-Id: Ia1c1b8adda0cd3eb07f3dbe7da2bd0b3fed265bf
diff --git a/jenkins/gerrit-buck-bazel-plugin-project-group-structure.yaml b/jenkins/gerrit-buck-bazel-plugin-project-group-structure.yaml
index e75ff63..16a6203 100644
--- a/jenkins/gerrit-buck-bazel-plugin-project-group-structure.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-project-group-structure.yaml
@@ -7,5 +7,6 @@
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
+            - stable-2.16
             - stable-2.15
             - stable-2.14