Build groovy-provider on Gerrit 2.15

Change-Id: Ie38d26ee3cb73bc7f43db765d0c5140ee01bede2
diff --git a/jenkins/gerrit-buck-bazel-plugin-groovy-provider.yaml b/jenkins/gerrit-buck-bazel-plugin-groovy-provider.yaml
index 94fe151..eefe8b2 100644
--- a/jenkins/gerrit-buck-bazel-plugin-groovy-provider.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-groovy-provider.yaml
@@ -11,4 +11,5 @@
             - master
           gerrit-branch:
             - master
+            - stable-2.15
             - stable-2.14