Streamfield image output as original

[Dan Braghiș]

Best to avoid this and use a proper rendition

[Thibaud Colas]

I see renditions for all block types rendered in https://github.com/wagtail/wagtail.org/blob/next/wagtailio/core/templates/core/includes/streamfield.html, so will assume we’re good for the to-be-launched redesign.