RichTextAreaElement#dropFile leaves an unlabelled file input in the page

RichTextAreaElement#loadFile, in the CKEditor test page objects, appends an <input type="file"> to the page body to load the dropped file, and never removes it. When the page is not reloaded afterwards, e.g. after saving from the in-place edit mode, the next WCAG validation reports it as "Form elements must have labels".

This happens in InplaceEditIT#dropNonImageFile, on the attachments pane after save.

The input should be removed once the drop event has been dispatched.