Avoid systemd_requires as per updated packaging guidelines
    
    There is no need to have them as systemd correctly handles reloading
    depending on the transaction ordering (even if systemd is installed
    _after_ the package that installs the unit file).
    
    Additionally, this also drops hard requires on /usr/bin/systemctl and
    just makes the scriptlets that call systemctl conditional on systemctl
    being present.
    
    All of this helps avoid pulling in full systemd for container setups.