Fix for Alex's changes.

Author: lucadegasperi

src/Storage/FluentAdapter.php

@@ -11,10 +11,10 @@
 
 namespace LucaDegasperi\OAuth2Server\Storage;
 
-use League\OAuth2\Server\Storage\Adapter;
+use League\OAuth2\Server\Storage\AbstractStorage;
 use Illuminate\Database\ConnectionResolverInterface as Resolver;
 
-abstract class FluentAdapter extends Adapter
+abstract class FluentAdapter extends AbstractStorage
 {
     /**
      * @var \Illuminate\Database\ConnectionResolverInterface