[CI] move queue setting to project level

Jobs are currently not running. Fix as described in [1][2]

[1] https://lists.opendev.org/pipermail/service-announce/2022-September/000044.html
[2] https://lists.zuul-ci.org/pipermail/zuul-discuss/2022-May/001801.html

Change-Id: I92d1cb6d78a1a12bd0fb52699f1007645a666df9

.zuul.yaml

@@ -50,6 +50,7 @@
     timeout: 2400
 
 - project:
+    queue: magnum
     templates:
       - openstack-cover-jobs
       - openstack-python3-yoga-jobs
@@ -61,7 +62,6 @@
         - magnum-tempest-plugin-tests-api
         - magnum-container-build
     gate:
-      queue: magnum
       jobs:
         - magnum-tempest-plugin-tests-api
     post: