Allow unnormalized types in drop elaboration
I work on a [rustc driver](https://github.com/AeneasVerif/charon) that aims to extract the full polymorphic MIR of a crate. Currently the one thing I can't get is drop glue because it fails on unnormalizable types like the fields of `Cow` or `NonZero`.
This PR removes the one check for unnormalized types in drop elaboration. It's a `span_delay_bug` so only there to help catch mistakes. I think that's fine to remove? If something downstream relies on types being normalized the right approach is for MIR validation to check for normalized types, not that one random check.
60ed1ab0ec