password-dialog: Don't map Esc to window.close
AdwDialog handles Escape for us, and the dialog isn't a window so
window.close
isn't necessarily what we want. It's not actually a bug
right now (I guess AdwDialog prevents the Escape key event from bubbling
up), but in the future if something changes, then emitting window.close
might just close the entire GNOME Settings window
Follow-up for !2529 (merged)