i3 MK3S+ better fan shroud

The hole for the fan and mounting remained the same, I'm not sure if it's a remix. The original, together with the silicone sock, blows on the heat block and in front of the nozzle. This version blows under the nozzle from three sides, I verified it on a glass of water and also on the "pin support challenge" printout. I now print this bit of the extruder mainly from nylon and it has not melted since then. I gave supports only after the bridges of three exhalations. It is good to slow down the print to the last five millimeters of height, otherwise the filament will not have time to cool down.