Revert "config: disable ppc64le architecture for now"

We have access to the ppc64le builder from the new cluster, so we can
add ppc64le back into the list of additional arches.

This reverts commit 6ba2082.

Author: marmijo

config.yaml

@@ -22,7 +22,7 @@ streams:
   # bodhi-updates-testing:
   #   type: mechanical
 
-additional_arches: [aarch64, s390x]
+additional_arches: [aarch64, ppc64le, s390x]
 
 source_config:
   url: https://github.com/coreos/fedora-coreos-config