Surface Height is smoothed by default and shouldn't be

[AlexisRenchon]

As discussed on JuliaLang Slack #Makie,
there is currently a problem with Makie.surface:
Heights are smoothed, in the figure below you can see a rectangle at z = 2, surface should also be at z = 2 but isn't.
I tested to update the rectangles and surface nodes to, for example, z = 3, z = 4... which moves the rectangle and the surface, but the surface stays a bit too low.