pyca cryptography removed int_from_bytes, so it need to be removed from preque check

[orangepizza]

https://github.com/pyca/cryptography/pull/6652/files
function int_from_bytes in cryptography.util will be removed form cryptography 37.0, which will be released in April 26ish, which will break stem's cryptography detection because it try to import them
thoses int from/to bytes isn't really used, so we can safely remove them

[FedericoCeratto]

This impacts onionbalance - see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1026470

[atagar]

Hi Federico. As discussed on a couple other issues (#126 and #127) you'll need to contact 'gk at torproject dot org' if you'd care for this to change.