Classes automatically added to the link: 'file', 'file--mime-[MIME_TYPE]', 'file--[GENERIC_MIME_TYPE]' in EditorFileDialog.php not being added on the upload file <a> element

Attached patch fixes the issue and classes are properly added

@yara mezher
thank you for your contribution.
Can you please create a merge request to speedup reviewing and testing process?
here's how: https://www.drupal.org/community/contributor-guide/task/create-a-merge-r... →

Created MR, please review it.

Thanks!