fedora-eln-release should not set VARIANT[_ID] in os-release

[sgallagher]

The VARIANT and VARIANT_ID fields in /usr/lib/os-release are there to indicate a divergence from the standard or expected release. We don't (currently) offer variants of ELN; there's just the one configuration.

[yselkowitz]

Technically true, but I wonder what else is relying on VARIANT=eln and how much more would break as a result?