zuul: Declare queue at top level

Zuul deprecated declaring shared queues at a pipeline level with
release 4.1.0[1]. This updates the job definition to use the top level
declaration instead.

See [2] for details.

[1] https://zuul-ci.org/docs/zuul/latest/releasenotes.html#relnotes-4-1-0-deprecation-notes
[2] http://lists.openstack.org/pipermail/openstack-discuss/2022-May/028603.html

Change-Id: Ie63dd3b161cb8fd9be89002027d699ce2c4a67a5
(cherry picked from commit 4212950a4a)

.zuul.d/project.yaml

@@ -1,4 +1,5 @@
 - project:
+    queue: horizon
     templates:
       - check-requirements
       - horizon-cross-jobs
@@ -16,7 +17,6 @@
         - horizon-tox-bandit-baseline
         - horizon-tempest-plugin-ipv6
     gate:
-      queue: horizon
       jobs:
         - horizon-dsvm-tempest-plugin
         - horizon-selenium-headless