Backspace is not removing items from the field

Problem/Motivation

When the backspace is being pressed, no items are being removed. The autocomplete_deluxe.js code has some handling for the backspace, called inside the keypress event. I don't know if this has ever worked, as keypress event

is fired when a letter, number, punctuation, or symbol key is pressed

https://developer.mozilla.org/en-US/docs/Web/API/Element/keypress_event

It's also deprecated and should be replaced with keydown.

Steps to reproduce

Enter some things with the autocomplete deluxe widget. Press backspace to get rid of items. Items are not deleted.

Proposed resolution

Replace keypress with keydown.

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API changes

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