Dropped CentOS8-based TripleO job

No RDO release for CentOS8 will get a OpenStackSDK 1.x.x release.

Change-Id: I728f0f282717c11a782be30859f999008f3fc8cb

.zuul.yaml

@@ -299,8 +299,8 @@
 
 # TripleO jobs
 - job:
-    name: tripleo-ci-centos-8-standalone-osa
-    parent: tripleo-ci-centos-8-standalone-build
+    name: tripleo-ci-centos-9-standalone-osa
+    parent: tripleo-ci-centos-9-standalone-build
     branches: master
     vars: &tripleo_vars
       consumer_job: false
@@ -351,15 +351,6 @@
       - ^plugins/modules/stack.*$
       - ^plugins/modules/subnet.*$
 
-- job:
-    name: tripleo-ci-centos-9-standalone-osa
-    parent: tripleo-ci-centos-9-standalone-build
-    branches: master
-    vars: *tripleo_vars
-    required-projects: *tripleo_required_projects
-    irrelevant-files: *tripleo_irrelevant_files
-    files: *tripleo_files
-
 - job:
     name: ansible-collections-openstack-release
     parent: base
@@ -444,7 +435,6 @@
 
     experimental:
       jobs:
-        - tripleo-ci-centos-8-standalone-osa
         - ansible-collections-openstack-functional-devstack-ansible-2.11
 
     tag: