Build metrics-reporter-cloudwatch against stable-3.3

Feature: Issue 13713
Change-Id: I6b7d6b3d96c7026b1206d9bfa3145604727799f1
diff --git a/jenkins/gerrit-bazel-plugin-metrics-reporter-cloudwatch.yaml b/jenkins/gerrit-bazel-plugin-metrics-reporter-cloudwatch.yaml
index 7bdfbe4..e69168e 100644
--- a/jenkins/gerrit-bazel-plugin-metrics-reporter-cloudwatch.yaml
+++ b/jenkins/gerrit-bazel-plugin-metrics-reporter-cloudwatch.yaml
@@ -4,4 +4,5 @@
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
+            - stable-3.3
             - stable-3.2