Fix Issue 3217: Remove download link for a "new version" of a deleted file.

We don't show the orig revision or a download link for it for new files, so we
probably shouldn't show the new revision or a download link for deleted files,
either.

Testing Done:
* Created a review with a deleted file.
* Download link for a new revision of a deleted file no longer appears in the
  file revision header.
* Headers for modified and new files remain unchanged.

Bugs closed: 3217

Reviewed at https://reviews.reviewboard.org/r/5377/