tang does not necessarily require systemd, as it can run standalone. systemd, however, is almost always available, unless in some specific situations, like containers.

Let's weaken the systemd dependency in tang, so that it will not pull systemd in scenarios like containers, reducing its footprint (and attack surface).

The change is to use %{?systemd_ordering} instead of %{?systemd_requires} in tang spec file, which means that we want to use systemd tools if they are available,
but do not want to declare a dependency [1].

[1] https://docs.fedoraproject.org/en-US/packaging-guidelines/Scriptlets/#_dependencies_on_the_systemd_package

AC: Make sure tang spec file has %{?systemd_ordering} instead of %{?systemd_requires}