fix(style): remove unused Collection class

Author: bernard-ng

src/Client.php

@@ -4,7 +4,6 @@
 
 namespace Devscast\Pexels;
 
-use Devscast\Pexels\Data\Collection;
 use Devscast\Pexels\Data\CollectionMedia;
 use Devscast\Pexels\Data\Collections;
 use Devscast\Pexels\Data\Photo;