Printrbot Simple Metal Cable Spring

The cable that runs to the printhead sometimes gets in the way, particularly when lowering the printhead after tall prints. This simple spring helps make sure it stays out of the way.

This is based loosely on https://www.thingiverse.com/thing:356011 -- I saw it, closed the browser tab, and then couldn't find it again, so designed my own. On finding mgx's design again, I think I prefer my ends.