Add job for building replication plugin with Buck

The stable-2.13 branch is still built with Buck, so add a job for it, should we need to apply fixes on the stable branch.

Change-Id: Ib0dacff36e954c0e4ec69209a854610519db5423
diff --git a/jenkins/gerrit-buck-bazel-plugin-replication.yaml b/jenkins/gerrit-buck-bazel-plugin-replication.yaml
index 94f1731..9fa5702 100644
--- a/jenkins/gerrit-buck-bazel-plugin-replication.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-replication.yaml
@@ -1,6 +1,9 @@
 - project:
     name: replication
     jobs:
+      - 'plugin-{name}-{branch}':
+          branch:
+            - stable-2.13
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master