audio/praat: update to 6.4.67, latest upstream
Release notes as always at
https://www.fon.hum.uva.nl/praat/manual/What_s_new_.html
The build system has been revamped (in unfortunate ways), I ought to
engage with upstream to get it to build well with meson on FreeBSD,
so we can abandon all the Makefile hacks.