Do not revert 3D scatter to 2D if multiple 3D plots present in figure.

[BRONSOLO]

A user wrote in with a figure that contained a 3D surface + contour line projected onto the z=0 xy-plane. The parser interpreted these projections as 2D because of this: https://github.com/plotly/MATLAB-api/blob/master/plotly/plotlyfig_aux/handlegraphics/updateScattergroup.m#L86-L90 (a workaround for some 2D plots that contain Z data which is set to be entirely zero). We do not support 2D + 3D mixed plots so this figure did not render. We could probably get around this by checking to see if the figure contains multiple 3D plots and if so, trying to render everything as 3D.