Build gitiles plugin stable-2.15 separately

Change-Id: I4b0014874d1ee18e584a0a2568843e8b7c97c6b5
diff --git a/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml b/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml
index b826245..cdbba94 100644
--- a/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-gitiles.yaml
@@ -15,10 +15,6 @@
             - stable-2.10
       - 'plugin-{name}-bazel-{branch}':
           branch:
-            - stable-2.14
-      - 'plugin-{name}-bazel-{branch}-{gerrit-branch}':
-          branch:
-            - master
-          gerrit-branch:
             - master
             - stable-2.15
+            - stable-2.14