Always evaluate with config.allowAliases = false to avoid deprecation warning errors #575
Description
Since #250, we've been checking that Nixpkgs doesn't depend on aliases.
In NixOS/nixpkgs#134230 I've had to revert deprecation warnings in order to let ofborg evaluate cleanly.
If we apply allowAliases = false to all evaluations, we will be able to provide helpful deprecation warnings without causing ofborg to fail.
It will also save an evaluation, because the separate check from #250 will be implicit in the other evals.