Update 'latest' definitions to f38, correct fedora-38-container
    
    F38 is the 'latest' release now, F36 is EOL. Also, the
    fedora-38-container definition was still using zuul-worker-f37,
    which seems wrong, change it to f38.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>