Build git-repo-metrics master against Gerrit stable-3.7

Change-Id: Ifac6efed874ad5d99d24dee5da9910375315d792
diff --git a/jenkins/gerrit-bazel-plugin-git-repo-metrics.yaml b/jenkins/gerrit-bazel-plugin-git-repo-metrics.yaml
index 9c1fdb7..1409272 100644
--- a/jenkins/gerrit-bazel-plugin-git-repo-metrics.yaml
+++ b/jenkins/gerrit-bazel-plugin-git-repo-metrics.yaml
@@ -5,6 +5,7 @@
           branch:
             - master
           gerrit-branch:
+            - stable-3.7
             - stable-3.6
             - stable-3.5
             - stable-3.4