Run ELN tests on BIOS
    
    ELN can't boot with Secure Boot enabled currently:
    https://github.com/fedora-eln/eln/issues/183
    
    Until that's resolved, let's go back to testing on BIOS (this is
    easier than testing on non-SB UEFI for...reasons).
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>