Improved Optical Filament Runout Sensor

I combined the original sensor with a mount (see https://www.thingiverse.com/thing:4055649), but when I had filament run out during a recent print, the end of the filament got stuck in the sensor. I had to disassemble it and pull the remainder out with pliers.

This remix does two things: it puts a "funnel" on the inlet that should direct the loose end back out of the sensor when your printer ejects the filament, and it enlarges the filament holes so that they should print at the right size. (It worked for ABS, and it'll probably work for PLA, but the holes might need to be opened up even more for PETG. I'll know more in a bit.)