audio/sndio: Update to 1.4.0
There are no code changes in libsndio, but the major/minor of libsndio
was bumped to 7.0 in this release to match libsndio on OpenBSD
regardless. On OpenBSD some private symbols were hidden via a version
script. This is not yet part of the portable release. Avoid causing
unnecessary churn and keep using 6.1 for the time being.