audio/libsndfile: set PORTREVISION for Fix CVE-2022-33065

From: Masachika ISHIZUKA <ish_at_amail.plala.or.jp>
Date: Thu, 09 Nov 2023 06:41:21 UTC
  Hi.

  audio/libsndfile was fixed for CVE-2022-33065 in a1f663e8d4a65bdb5366a7992ebe02476a9d18c7.
  Please set PORTREVISION in Makefile.
-- 
Masachika ISHIZUKA