Replace direct mention of laravel application class by application contract

Author: Alexandru Doras

src/Illuminate/Database/Eloquent/Factories/Factory.php

@@ -7,7 +7,7 @@
 use Illuminate\Container\Container;
 use Illuminate\Database\Eloquent\Collection as EloquentCollection;
 use Illuminate\Database\Eloquent\Model;
-use Illuminate\Foundation\Application;
+use Illuminate\Contracts\Foundation\Application;
 use Illuminate\Support\Collection;
 use Illuminate\Support\Str;
 use Illuminate\Support\Traits\ForwardsCalls;