misc/mnn: Update the tarball because it was re-released by the upstream

The previous port update was at 2020-01-16 06:55:46Z, so the previous verion of this release was made before this time.
This re-release was made, according to GitHub, at 2020-01-17 04:08:00 PST (2020-01-17 12:08:00Z).

Reported by: fallout