Remove @file doc block from code base

As per the recent coding standards we need to remove the @ file doc annotation.

We still need @file in .module and .install files, as well as theme templates.
The only @file doc blocks to remove would be for files under (modulename)/src -- the PSR-4-compliant class/interface files.

From https://www.drupal.org/coding-standards/docs:

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.

See #2723077: Removing @file doc block from code base