Remove redundant Requires(pre)
    
    The %sysusers_requires_compat RPM macro already covers this because it
    evaluates to:
      Requires(pre): shadow-utils
    
    Fallout from dd0498ebb79605ee6a18100db30b07fddfaf31e4
    
    https://src.fedoraproject.org/rpms/munge/pull-request/4