Use template for lower-constraints

Small cleanups:

* Use openstack-lower-constraints-jobs template, remove individual
  jobs.
* Sort list of templates

Change-Id: I67199fabe6a9f7b1fd38dac77a6157bf4fb465b9
Needed-By: https://review.openstack.org/623229

zuul.d/project.yaml

 ---
 - project:
     templates:
+      - check-requirements
+      - deploy-guide-jobs
+      - openstack-cover-jobs
+      - openstack-lower-constraints-jobs
       - openstack-python-jobs
       - openstack-python35-jobs
       - openstack-python36-jobs
-      - openstack-cover-jobs
-      - check-requirements
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
-      - deploy-guide-jobs
     check:
       jobs:
         - kolla-ansible-centos-source
@@ -21,12 +22,10 @@
             files: ^ansible\/roles\/bifrost\/.*
         - kolla-ansible-ubuntu-source-zun:
             files: ^ansible\/roles\/zun\/.*
-        - openstack-tox-lower-constraints
     gate:
       jobs:
         - kolla-ansible-centos-source
         - kolla-ansible-ubuntu-source
-        - openstack-tox-lower-constraints
     periodic:
       jobs:
         - kolla-ansible-bifrost-centos-source