bots: Stop releasing into Fedora 27
bots: Stop releasing into Fedora 27

Fedora 28 is released now.

Closes #9087
stefwalter/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,deryni/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,mareklibra/cockpit,andreasn/cockpit,mvollmer/cockpit,stefwalter/cockpit,stefwalter/cockpit,cockpituous/cockpit,mvollmer/cockpit,martinpitt/cockpit,cockpituous/cockpit,mareklibra/cockpit,stefwalter/cockpit,andreasn/cockpit,deryni/cockpit,andreasn/cockpit,SotolitoLabs/cockpit,andreasn/cockpit,stefwalter/cockpit,deryni/cockpit,SotolitoLabs/cockpit,moraleslazaro/cockpit,deryni/cockpit,deryni/cockpit,mareklibra/cockpit,garrett/cockpit,cockpituous/cockpit,stefwalter/cockpit,cockpituous/cockpit,cockpituous/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,mvollmer/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,stefwalter/cockpit,SotolitoLabs/cockpit,garrett/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,mareklibra/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,deryni/cockpit,garrett/cockpit,mareklibra/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,andreasn/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,andreasn/cockpit,andreasn/cockpit,mareklibra/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,martinpitt/cockpit