Greg's X-Ends without Upper Nut Trap

This is a simple modification to GregFrost's excellent Prusa X-ends that removes the column for the upper nut trap. I don't use top nuts, so printing the nut traps would have been a waste of plastic and time.

This was a direct modification to the STL file, so there is no openscad or solidworks "source" file.

The STL has already been run through netfabb, so it shouldn't produce any errors.