Authors/authorids cannot be removed from the submission revision stage

[racheljsmart]

When author reorder is selected, authors and authorids fields are always being added back to the invitation from the notes.

Allow addition and deletion of authors in the submission revision stage and try to remove those two fields.

• add validation or don't add the authors/authorids if the reorder is selected but the fields were removed

[melisabok]

Check if the fields were removed here: https://github.com/openreview/openreview-py/blob/44ab347d4dd6f2e8585cc45da47e483c18e3d18f/openreview/conference/invitation.py#L744