Add stable-2.14 branch for x-docs

Change-Id: I1dc46925c64af0d8101a3201e0cf3c65a93ed83a
diff --git a/jenkins/gerrit-buck-bazel-plugin-x-docs.yaml b/jenkins/gerrit-buck-bazel-plugin-x-docs.yaml
index 66bf169..6dad719 100644
--- a/jenkins/gerrit-buck-bazel-plugin-x-docs.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-x-docs.yaml
@@ -9,3 +9,4 @@
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
+            - stable-2.14