handbook/sockets: Update time.nist.gov IP address

It has not been this IP address since 2012.

% drill -x 192.43.244.18
... this.has.not.been.ntp.server.time.nist.gov.since.2012.

Update it to 132.163.96.1.

Reviewed by: ziaee
Pull Request: https://github.com/freebsd/freebsd-doc/pull/563