Update extrusion examples to use separate fill-extrusion type

[lbud]

Update extrusion-based examples (once #3487 is merged). Refs mapbox/mapbox-gl-style-spec#554.

[jfirebaugh]

Can you retarget this at master, so that it goes live simultaneously with 0.27.0 being released?

[lbud]

@jfirebaugh I'm not sure how the relationship between master and mb-pages works — I targeted here based on release documentation I was going through the other day. Should I still retarget at master?

[jfirebaugh]

There's more explanation here -- this case is admittedly borderline, since we're making a breaking change to an existing property. But I think it's better overall if we don't have a period of time where the published example won't work with the current released version, which would happen if we pushed to mb-pages before releasing 0.27.0.

[lbud]

@jfirebaugh makes sense, thanks 🙏

[lucaswoj]

This is good to merge alongside #3487. It might even make sense to combine the two branches before merging into master.