Switch to openstack-python3-zed-jobs job template

openstack-tox-py37 job comes from openstack-python3-ussuri-jobs
job template and is currently failing against
tripleo-operator-ansible project.

This job is already dropped from all tripleo projects and
it does not make sense to maintain it as py39 job is
already running.

That's why we are switching to openstack-python3-zed-jobs
job template.

Signed-off-by: Chandan Kumar (raukadah) <chkumar@redhat.com>
Change-Id: I4dddd31740c6ab22a8152379510b84f48044344d

zuul.d/layout.yaml

@@ -24,7 +24,7 @@
 
 - project:
     templates:
-      - openstack-python3-ussuri-jobs
+      - openstack-python3-zed-jobs
       - tripleo-operator-molecule-jobs
       - release-notes-jobs-python3
     check:
@@ -34,8 +34,7 @@
             dependencies:
               - openstack-tox-linters
               - openstack-tox-pep8
-              - openstack-tox-py36
-              - openstack-tox-py37
+              - openstack-tox-py39
             files: &content_provider
               - ^roles/tripleo_undercloud_install/.*$
               - ^roles/tripleo_deploy/.*$