idn2: unrecognized option '--nostd3asciirules'

Seen with libidn2 2.0.4:

$ idn2 --help
…
      --nostd3asciirules   Disable STD3 ASCII rules
…

But:

$ idn2 --nostd3asciirules
idn2: unrecognized option '--nostd3asciirules'
$

Initially reported at https://bugzilla.redhat.com/show_bug.cgi?id=1543010