relaxed `?Sized` bound getting implied by super trait warn

[lcnr]

the following code should lint that the ?Sized bound is unused:'

trait Proj {
    type Assoc: Clone + ?Sized;
}

fn foo<T: ?Sized + Clone>() {}

we imply Sized as it's a super trait of Clone, so the ?Sized bound does not do anything.

cc @davidtwco, related to sized_hierarchy migration stuff

[davidtwco]

Had a brief look at this to see what it would involve - Clippy already has this lint so we really just need to uplift it - https://rust-lang.github.io/rust-clippy/master/index.html#/needless_maybe

[lcnr]

👍 alright, I would love for this to happen and would be very happy if somebody were to do this. As a starting point, consider looking at previous uplift PRs to figure out the process.

[CrooseGit]

@rustbot claim
@davidtwco is mentoring me on this