`clippy::unused_label` has overlap with `unused_labels`

If there is an unused label in the code, you have to allow both the `rustc` lint, `unused_labels`, as well as the clippy lint of nearly the same name: `clippy::unused_label`.

The `clippy::unused_label` should be moved to allow by default during the deprecation period since `rustc` is covering the same thing now.
