Update instructions and renders for remove brim and ties when preparing the main body
Step 1: Removing brim and supports in the instructions for Prepare the main body has renders where it is not clear which parts are which.
The parts to remove are the brim, the actuator ties and the ties on the rear legs. This MR creates three separate renders for the three steps. In each render only one of the items is marked red, in order to make it clear.