Fedora ELN chroots are available in Copr

[Pavel Raiskup]

Since the new mock-core-configs are in Fedora stable, it allowed us to enable
fedora-eln-<arch> [1] buildroots in Fedora Copr.  Feel free to try them.

Note that Fedora ELN repositories aren't mirrored at this moment, and thus
we can face some weird repo/package downloading issues (as e.g. discussed
today in [2]).  We'll see.

[1] https://docs.fedoraproject.org/en-US/eln/
[2] https://github.com/rpm-software-management/mock/issues/614

Happy building!
Pavel