Fix return type for setTransformer() and setSerializer

Author: Sébastien Nikolaou

src/DataTableAbstract.php

@@ -15,8 +15,8 @@
 use Yajra\DataTables\Utilities\Helper;
 
 /**
- * @method DataTableAbstract setTransformer($transformer)
- * @method DataTableAbstract setSerializer($transformer)
+ * @method static setTransformer($transformer)
+ * @method static setSerializer($transformer)
  *
  * @property-read mixed $transformer
  * @property-read mixed $serializer