CLONE - In assignments with file uploading enabled the Student can upload files using drag and drop

Test Pre-requisites:

• A new 2.3 Assignment with file submissions enabled.

Test Steps:
1. Login as a student and navigate to the Assignment. Click the 'Edit my submission button' and verify that the File manager form element is displayed onscreen.
2. Drag and drop a file onto the file manager, which currently contains the text 'No files attached drag and drop files here to upload them.'
3. Click 'Save changes' and verify that the files have been uploaded.
4. Download the file to verify that the file link has been created properly.
5. Login as a Teacher and download the file, then verify that the file is correct.