Remove duplicate interface implementation (laravel#14515)

Because the interface `QueueingDispatcher`   inherits from the interface `Illuminate\Contracts\Bus\Dispatcher`, there is no need to implement the interface `Illuminate\Contracts\Bus\Dispatcher` again.

src/Illuminate/Bus/Dispatcher.php

@@ -9,9 +9,8 @@
 use Illuminate\Contracts\Queue\ShouldQueue;
 use Illuminate\Contracts\Container\Container;
 use Illuminate\Contracts\Bus\QueueingDispatcher;
-use Illuminate\Contracts\Bus\Dispatcher as DispatcherContract;
 
-class Dispatcher implements DispatcherContract, QueueingDispatcher
+class Dispatcher implements QueueingDispatcher
 {
     /**
      * The container implementation.