Build delete-project plugin on Gerrit v2.15

Change-Id: Ifbda39e06743986d493f3828d13281a8218e7975
diff --git a/jenkins/gerrit-buck-bazel-plugin-delete-project.yaml b/jenkins/gerrit-buck-bazel-plugin-delete-project.yaml
index 8a0acd0..be7310f 100644
--- a/jenkins/gerrit-buck-bazel-plugin-delete-project.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-delete-project.yaml
@@ -9,5 +9,10 @@
             - stable-2.10
       - 'plugin-{name}-bazel-{branch}':
           branch:
-            - master
             - stable-2.14
+      - 'plugin-{name}-bazel-{branch}-{gerrit-branch}':
+          branch:
+            - master
+          gerrit-branch:
+            - master
+            - stable-2.15