Remove centos-stream-8 from ansible builds

For various reasons, the centos-stream-8 container
points to a set of invalid mirrorlists.  Upstream
has not chosen to clean this up.  While it would
be possible to adjust the workflow steps to adjust
for this, just eliminate the build, as other than
a few uninstalled packages (such as the kernel and
grub), rocky-8 (which we also build) covers all
the same packages.

.github/workflows/ansible.yml

@@ -74,9 +74,6 @@ jobs:
             ansibleopts: '--limit localhost'
 
           # CentOS group
-          - desc: 'CentOS 8 Stream'
-            image: 'quay.io/centos/centos:stream8'
-            ansibleopts: '--limit localhost'
           - desc: 'CentOS 9 Stream'
             image: 'quay.io/centos/centos:stream9'
             ansibleopts: '--limit localhost'