audio/piper-phonemize: Correct COMMENT

It was just copied from audio/piper. Piper is a "Fast, local neural
text to speech system" while piper-phonemize is one of its dependencies.

Reviewed by: jrm
Event: Halifax Hackathon 202606
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D57819