Bump FFmpeg to version 7

[luukvandervelden]

@patrickkfkan develops a Soundcloud plugin for Volumio. While investigating high quality streams of a Soundcloud Go+ subscription, he found that the streams have the following two formats:

1. HLS + AAC: plays in Volumio, but will crash / cause MPD to become unresponsive if you try to seek.
   

2. Progressive + AAC: does not play in Volumio whatsoever.
   

Further he tried playing the HQ streams on another machine running MPD + FFmpeg 7.0. HLS + AAC is not much different, but Progressive + AAC plays fine (and seek works too).

Volumio still uses FFmpeg 4.1.11. Would you update to FFmpeg 7.0?