Build metrics-reporter-prometheus for Gerrit on stable-3.3

Build the master branch of metrics-reporter-prometheus against
the stable-3.3 branch of Gerrit.

Change-Id: If9a2d88b3e231d2517f9ec3ff54c558cbb6c2a31
diff --git a/jenkins/gerrit-bazel-plugin-metrics-reporter-prometheus.yaml b/jenkins/gerrit-bazel-plugin-metrics-reporter-prometheus.yaml
index ad23d05..0531e49 100644
--- a/jenkins/gerrit-bazel-plugin-metrics-reporter-prometheus.yaml
+++ b/jenkins/gerrit-bazel-plugin-metrics-reporter-prometheus.yaml
@@ -5,10 +5,11 @@
           branch:
             - master
           gerrit-branch:
-            - master
+            - stable-3.3
             - stable-3.2
             - stable-3.1
             - stable-3.0
       - 'plugin-{name}-bazel-{branch}':
           branch:
+            - master
             - stable-2.16