Add stable-2.14 and stable-2.15 branch for its-base

Change-Id: Id761b1e14b058b018a2a586bf370044fb9812a35
diff --git a/jenkins/gerrit-buck-bazel-plugin-its-base.yaml b/jenkins/gerrit-buck-bazel-plugin-its-base.yaml
index 8e265a5..86b4d29 100644
--- a/jenkins/gerrit-buck-bazel-plugin-its-base.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-its-base.yaml
@@ -7,10 +7,9 @@
             - stable-2.12
             - stable-2.11
             - stable-2.10
-      - 'plugin-{name}-bazel-{branch}-{gerrit-branch}':
+      - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
-          gerrit-branch:
-            - master
+            - stable-2.15
             - stable-2.14
           targets: 'plugins/its-base:its-base plugins/its-base:its_base_tests'