[CI] Stop testing non-stream CentOS

Per [1].
It was agreed on during a Kolla IRC meeting. [2]

This continues building non-stream images as they are built on
CentOS 7.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2021-December/026408.html
[2] https://meetings.opendev.org/meetings/kolla/2021/kolla.2021-12-22-15.01.log.html#l-53

Change-Id: I6bbd4c574db190bea2603ce0761dbc31f8745242

.zuul.d/centos.yaml

@@ -7,9 +7,7 @@
         - kolla-build-centos8-binary
         - kolla-build-centos8-source
         - kolla-ansible-centos-source
-        - kolla-ansible-centos8-source
         - kolla-ansible-centos-binary
-        - kolla-ansible-centos8-binary
         - kolla-ansible-centos-source-upgrade
         - tripleo-build-containers-centos-7:
             voting: true
@@ -25,7 +23,6 @@
         - kolla-build-centos-source
         - kolla-build-centos8-source
         - kolla-ansible-centos-source
-        - kolla-ansible-centos8-source
         - kolla-ansible-centos-source-upgrade
         - tripleo-build-containers-centos-7:
             voting: true
@@ -51,8 +48,6 @@
       jobs:
         - kolla-ansible-bifrost-centos-source:
             files: ^docker\/(base|bifrost|openstack-base)\/.*
-        - kolla-ansible-centos8-source-bifrost:
-            files: ^docker\/(base|bifrost|openstack-base)\/.*
         # Test rabbitmq & mariadb changes in multinode ceph jobs.
         - kolla-ansible-centos-source-ceph:
             files: ^docker\/(base|ceph|cinder|glance|mariadb|openstack-base|rabbitmq)\/.*
@@ -60,16 +55,10 @@
             files: ^docker\/(base|ceph|cinder|glance|mariadb|openstack-base|rabbitmq)\/.*
         - kolla-ansible-centos-source-zun:
             files: ^docker\/(base|cinder|etcd|iscsid|kuryr|openstack-base|zun)\/.*
-        - kolla-ansible-centos8-source-zun:
-            files: ^docker\/(base|cinder|etcd|iscsid|kuryr|openstack-base|zun)\/.*
         - kolla-ansible-centos-source-scenario-nfv:
             files: ^docker\/(base|barbican|heat|mistral|openstack-base|redis|tacker)\/.*
-        - kolla-ansible-centos8-source-scenario-nfv:
-            files: ^docker\/(base|barbican|heat|mistral|openstack-base|redis|tacker)\/.*
         - kolla-ansible-centos-source-ironic:
             files: ^docker\/(base|dnsmasq|ironic|ironic-inspector|iscsid|openstack-base)\/.*
-        - kolla-ansible-centos8-source-ironic:
-            files: ^docker\/(base|dnsmasq|ironic|ironic-inspector|iscsid|openstack-base)\/.*
 
 - job:
     name: kolla-build-centos-binary