Fix graphite build for Gerrit v2.15

With I9797edde all the metrics reporter have been
built for v2.15. However, a typo was left in the graphite one
getting an inexistent branch.

This fixes the typo and resume a successful build
for the graphite plugin on v2.15

Change-Id: I0d0a17378500174dd3e4cdc5cf0cad6357f3fcd7
diff --git a/jenkins/gerrit-buck-bazel-plugin-metrics-reporter-graphite.yaml b/jenkins/gerrit-buck-bazel-plugin-metrics-reporter-graphite.yaml
index c6e389a..d05e4e9 100644
--- a/jenkins/gerrit-buck-bazel-plugin-metrics-reporter-graphite.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-metrics-reporter-graphite.yaml
@@ -6,6 +6,10 @@
             - stable-2.13
       - '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