release.nix: disable test builds with GHC 7.11.x as they fail anyway
release.nix: disable test builds with GHC 7.11.x as they fail anyway

Our requires libraries aren't ready for that.

bennofs/cabal2nix,jb55/cabal2nix,gridaphobe/cabal2nix,spencerjanssen/cabal2nix,dmalikov/cabal2nix,psibi/cabal2nix,Fuuzetsu/cabal2nix