Dropdowns should not open/trigger on "ESC"

This seems to be a regression from 3.x (see https://github.com/twbs/bootstrap/issues/14646)

Currently, dropdowns https://getbootstrap.com/docs/4.3/components/dropdowns/ can be opened by setting focus to the trigger element and pressing the "ESC" key. It's not a major problem, but non-standard and unexpected behaviour, which should really be removed.