Updating `SubmissionBundler.bundle`.

Reverting treatment of `graphic`-matched lines when `strip_figures` is
`True`... again. These curently cannot be processed by
`finish_parsing_ref` to create a `LatexFigureRef` instance, because the
`figure` header line is most likely already been passed. To handle these
as `LatexFigureRef`s, I need to include the `figure` header pattern in
the line-by-line search within `bundle`, which I do not want to tackle
right now.

For now, simply skipping the `includegraphics` line in the output will
do.