Move fedora-indexer to production and remove regindexer
    
    * Update rsync configuration for production to sync the flatpak-indexer
      output directories into the right place, in the same way as was done
      for staging. The regindexer rsync module is renamed to flatpak-index
      for clarity.
    * Update the registry.fedoraproject.org to use the flatpak-indexer
      rules for production.
    * Remove the regindexer role
    
    Signed-off-by: Owen W. Taylor <otaylor@fishsoup.net>