Enable bootstrap for x86_64 as well
    
    It seems Fedora packages need to be bootstrapped for all architectures,
    or none. Trying to bootstrap for only one architecture leads to errors
    from koji:
    
        GenericError: srpm mismatch for .. : dotnet3.1-3.1.105-2.fc33~bootstrap.src.rpm (expected dotnet3.1-3.1.105-2.fc33.src.rpm)