Remove @file doc block from namespaced classes, interfaces and traits

The Drupal 8 coding standard guide states

The @file doc block MUST be present for all PHP files, with one exception: files that contain a namespaced class/interface/trait, whose file name is the class name with a .php extension, and whose file path is closely related to the namespace (under PSR-4 or a similar standard), SHOULD NOT have a @file documentation block.

https://www.drupal.org/coding-standards/docs#file