[CI] Stop checking TripleO

It has been confirmed [1] that TripleO does not rely on Kolla
since Ussuri.
The job has been long broken and this patch removes it from the
check queue for Kolla Ussuri.

[1] http://eavesdrop.openstack.org/irclogs/%23openstack-kolla/%23openstack-kolla.2021-01-22.log.html#t2021-01-22T16:30:13

Change-Id: I6a06607434b2e30d841d543ea2922f0c13d463f2

.zuul.d/centos.yaml

@@ -7,14 +7,6 @@
         - kolla-ansible-centos8-source
         - kolla-ansible-centos8-binary
         - kolla-ansible-centos8-source-upgrade
-        - tripleo-build-containers-centos-8:
-            voting: false
-            files:
-              - ^docker/.*$
-              - ^kolla/.*$
-              - ^requirements.txt$
-              - ^setup.cfg$
-              - ^setup.py$
     check-arm64:
       jobs:
         - kolla-build-centos8-source-aarch64