Upgrade Zuul

Change-Id: Ied0fd88aac44c579bca2e330d7e3bfba824f8324
diff --git a/roles/zuul_server/tasks/main.yaml b/roles/zuul_server/tasks/main.yaml
index e874b63..22421fe 100644
--- a/roles/zuul_server/tasks/main.yaml
+++ b/roles/zuul_server/tasks/main.yaml
@@ -60,7 +60,7 @@
     name: openstack.zuul
   vars:
     zuul_install_method: pip
-    zuul_git_version: '3.5.0'
+    zuul_git_version: '3.7.1'
     zuul_pip_executable: /opt/rh/rh-python36/root/bin/pip
     zuul_pip_extra_args: "--install-option='--install-scripts=/usr/local/bin'"
     zuul_file_zuul_conf_src: files/zuul/zuul.conf