Use feature/zuulv3 for zuul-migrate test

Change-Id: Ie75e752414415c1562519ae96bc852a1f7ff868b
diff --git a/.zuul.yaml b/.zuul.yaml
index e96bc5a..8794c4f 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -36,7 +36,8 @@
     # this from project-config changes
     required-projects:
       - openstack-infra/project-config
-      - openstack-infra/zuul
+      - name: openstack-infra/zuul
+        override-branch: feature/zuulv3
 
 - project:
     name: openstack-infra/zuul