zuul: Declare queue at top level

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

Change-Id: Ifd674efb349e0c3156606c8fce72a176f8d05b0f
(cherry picked from commit 84f11c7468)

zuul.d/layout.yaml

@@ -1,5 +1,6 @@
 ---
 - project:
+    queue: tripleo
     templates:
       - check-requirements
       - openstack-cover-jobs
@@ -9,4 +10,5 @@
       - tripleo-multinode-container-minimal-pipeline
       - tripleo-upgrades-master-pipeline
     gate:
-      queue: tripleo
+      jobs:
+        - openstack-tox-pep8