Jupyter notebook example: deprecated matplotlib function "set_smart_bounds"

Hi. Experimenting with codex, I found that the degree plotting function in the exploration notebook has a minor issue. matplotlib "set_smart_bounds" is deprecated. I found this approach to fix and I leave here for reference. Thanks for the nice dataset.

    ax.spines["left"].set_bounds(x.min(), x.max())
    ax.spines["bottom"].set_bounds(x.min(), x.max())