Fedora 36 is EOL, also opendev is dropping support for Fedora images
completely since interest in running jobs on that platform is no longer
existing. CentOS 9 Stream has evolved as replacement platform for new
features.

Only drop the Zuul configuration and the tag in stack.sh for now plus
update some docs. Cleanup of the deployment code will be done in a
second step.

Change-Id: Ica483fde27346e3939b5fc0d7e0a6dfeae0e8d1e