reverted:
--- b/core/modules/file/src/Plugin/migrate/cckfield/d6/FileField.php
+++ a/core/modules/file/src/Plugin/migrate/cckfield/FileField.php
@@ -2,10 +2,10 @@
 
 /**
  * @file
+ * Contains \Drupal\file\Plugin\migrate\cckfield\FileField.
- * Contains \Drupal\file\Plugin\migrate\cckfield\d6\FileField.
  */
 
+namespace Drupal\file\Plugin\migrate\cckfield;
-namespace Drupal\file\Plugin\migrate\cckfield\d6;
 
 use Drupal\migrate\Entity\MigrationInterface;
 use Drupal\migrate\Row;