Update to default NASSL version

[baknu]

NASSL now also supports TLS 1.3. So it seems we can use the default NASSL version instead of the patched NASSL version that we currently use.

See: https://github.com/nabla-c0d3/nassl

[sinteur]

@gthess do you know what patches are now covered in the default version?

[gthess]

No, haven't done a comparison with the upstream version since developing for TLS1.3.

[sinteur]

kay thx, I'll have a look then

[mxsasha]

See #714 for a wider view on this.

[mxsasha]

This is actually fully covered by #714 so closing this issue.