common.yaml: disable composefs on all arches

There are issues currently on ppc64le and kernel-64k in el9 that break
with composefs. So it's not sufficient to do an architecture check
anyway. See: https://issues.redhat.com/browse/RHEL-70199.

But additionally, there are issues also to resolve when dealing with
old bootimages. This should be fixed by turning on composefs image
generation by default in libostree and downgrading to `maybe` here. See:
openshift#1678.

Once we fix the latter issue, we should be able to turn it on at least
in the el10 variants, where the first issue doesn't exist. (Though
technically, even the latter issue is "fixed" in el10 by virtue of new
enough libostree in the bootimages, but it would still break to go from
an el9 bootimage to el10, which we'll likely have to support.)

common.yaml

@@ -60,11 +60,10 @@ postprocess:
   - |
     #!/usr/bin/bash
     set -xeuo pipefail
-    # Disable composefs for now on c9s/9.6 ppc64le due to
-    # https://issues.redhat.com/browse/RHEL-70199, which needs kernel backports.
-    if [ "$(uname -m)" = "ppc64le" ] && [[ $(rpm -q kernel) = *.el9.ppc64le ]]; then
-      rm -vf /usr/lib/ostree/prepare-root.conf
-    fi
+    # Disable composefs for now due to
+    # 1. ppc64le/kernel64k bugs: https://issues.redhat.com/browse/RHEL-70199
+    # 2. old bootimage concerns: https://github.com/openshift/os/issues/1678
+    rm -vf /usr/lib/ostree/prepare-root.conf
 
   # Mark the OS as of the CoreOS variant.
   # XXX: should be part of a centos/redhat-release subpackage instead