Build JavaMelody for Gerrit v2.9

Change-Id: Iba6b1d4be01dfaf8a539effa5fe0906161333363
diff --git a/jenkins/gerrit-buck-bazel-plugin-javamelody.yaml b/jenkins/gerrit-buck-bazel-plugin-javamelody.yaml
index 29f882c..9b3aa01 100644
--- a/jenkins/gerrit-buck-bazel-plugin-javamelody.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-javamelody.yaml
@@ -19,6 +19,7 @@
             - stable-2.12
             - stable-2.11
             - stable-2.10
+            - stable-2.9
           targets: >
             plugins/javamelody:javamelody-nodep
             plugins/javamelody:javamelody-deps