Rear Active Cooling Duct v3 for Qidi

Remix of the RACD V2 in order to fit the Qidi carriage. The Qidi has a solid edge running along the bottom of the carriage, which interferes with the boss lifted from the curve of the duct. This file has that boss removed, clearance added for the Qidi lip, and internal material added for additional strength in the resulting corner.

Snapped right onto the back of my carriage, and puts out some nice air onto the bed. With the longer extruders on the Qidi, this was the only duct I've found that