Revert %_smp_mflags patch to avoid breaking packages single-quoting it
    
    The original patch fixed a regression in 4.18.0 that affected
    reproducible builds in OpenSUSE but, at the same time, broke a couple of
    (Fedora) packages that relied on the %_smp_mflags value being static,
    such as those that use SPHINXOPTS='-j${RPM_BUILD_NCPUS}'.
    
    In the name of stability, we'll be better off just reverting this patch
    in F37 so that unexpected build failures in those packages are avoided.
    F38 and Rawhide do carry the original patch.
    
    More details at the URLs in the comments.