[Fedora-packaging] Guidelines update for "Packaging of Additional RPM Macros"

[Ville Skyttä]

https://fedoraproject.org/wiki/Packaging:Guidelines#Packaging_of_Additional_RPM_Macros

I suggest updating the first sentence of the above paragraph to:

Additional RPM macros must be stored under %{_rpmconfigdir}/macros.d
(%{_sysconfdir}/rpm on EL < 7) directory, [...]