Fix sorting in ` cargo dev update_lints` script
changelog: none
The old code cloned and sorted `usable_lints` into `sorted_usable_lints`, but then failed to do anything with `sorted_usable_lints`.
This was discovered by my new `collection_is_never_read` lint (#9267) that I'm working on!
Fix: I renamed the sorted vector to `usable_lints`. Therefore it now gets used where the unsorted one was used previously.