spotify: update ffmpeg version

Needed for spotify 1.1.x. The update itself is blocked on alsa issues:
https://community.spotify.com/t5/Desktop-Linux/spotify-client-1-1-0-98-78-gb45d2a6b-10-from-Ubuntu-package/td-p/4675676
https://community.spotify.com/t5/Desktop-Linux/1-0-98-1-1-0-Crash-when-using-ALSA/td-p/4680398