9abd80c076
As it was suggested in #81037 `SpecFromIter` is not in the scope and therefore (even it should fail), we get a warning when we try do document private intems in `rust/library/alloc/`. This fixes #81037 by adding the trait in the scope and also adding an `allow(unused_imports)` flag so that the compiler does not complain, Since the trait is not used per se in the code, it's just needed to have properly documented docs.