ruff

df9d6886 - [ty] Remove redundant `apply_specialization` type mappings (#22422)

[ty] Remove redundant `apply_specialization` type mappings (#22422) @dhruvmanila encountered this in #22416 — there are two different `TypeMapping` variants for apply a specialization to a type. One operates on a full `Specialization` instance, the other on a partially constructed one. If we move this enum-ness "down a level" it reduces some copy/paste in places where we are operating on a `TypeMapping`.