Incorrect FFMPEG path

[ripperdoc]

The path to ffmpeg-static should probably not use the subproperty .path, it doesn't seem to find it:

https://github.com/firebase/functions-samples/blob/207d80197711d14c93ff639ff8416c75f984c9e6/ffmpeg-convert-audio/functions/index.js#L69

If I change to .setFfmpegPath(ffmpeg_static) it works.