Errors in mount_motors.scad rendering

There are some errors in rendering/mount_motors.scad, that I mainly introduced during !333 (merged) (d6ba75bf). The manual body is always built, and ends up inside the other body when it is rendered motorised!

• remove lines 45-50 that always build the manual body
• set FRAME to a number that is a frame of this sequence (not 23)
• check indents (at least: lines 80-96, lines 90-95, 161-176)