Duet Wifi front mount for Kossel 2020

This is a trivial remix of the [Kossel 2020 mains inlet and electronics front panel](https://www.thingiverse.com/thing:965396) by [dc42](https://www.thingiverse.com/dc42/about), facilitated by his kind provision of the OpenSCAD source file. It simply removes the mains inlet part, leaving a board holder for the Duet Wifi electronics board that fits in a mini Kossel. The length has been adjusted to match his [Kossel 2020 electronics rear panel](https://www.thingiverse.com/thing:1617834).

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