Moots: use Schmitt trigger logic to debounce

[cosinekitty]

The current gate logic will not work correctly in some cases, especially if the gate input is band-limited. Gibbs rippling can cause multiple unintended toggling. Also, the threshold of 4V is too high.

Follow VCV Rack official gate voltage recommendations: use hysteresis (Schmitt trigger) to avoid unintentional rapid triggering. Turn on when gate voltage is between 1V-2V, turn off when gate voltage drops below 0.1V.