waiverdb: flip back to using factory2 container remote
    
    The fixes for https://github.com/release-engineering/waiverdb/issues/219
    were merged and the factory2 'latest' image now includes them.
    'prod-fedora' does not, so for now, we'll have prod use 'latest'
    instead.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>