[13.x] Ensure Queue::route string defaults to queue only

[jackbayliss]

As per https://github.com/laravel/docs/blob/545534afef3d8d0e350dbcb3dc97cc6c4b79f532/queues.md?plain=1#L1311

This ensures if it's only a string specified, it doesn't apply to the connection, only queue.

Technically could be considered a B/C, but I dont think it's a real one as this feels correct behavior.

This means the below works:

Queue::route([
   Job:class => 'queue'
]);

Added a test too.

[github-actions]

Thanks for submitting a PR!

Note that draft PRs are not reviewed. If you would like a review, please mark your pull request as ready for review in the GitHub user interface.

Pull requests that are abandoned in draft may be closed due to inactivity.

[taylorotwell]

Thanks!