README: Update playback example
README: Update playback example

We no longer require specifying the format of the audio manually.
raoulh/spotifile,catharsis/spotifile,raoulh/spotifile,chelmertz/spotifile,chelmertz/spotifile,catharsis/spotifile,raoulh/spotifile,catharsis/spotifile,chelmertz/spotifile