bump sample rate to 22256

this is the "correct" rate based on the original horizontal line rate of
the mac plus and is supported on the fruit jam i2s dac

src/main.c

@@ -768,7 +768,7 @@ struct audio_buffer_pool *producer_pool;
 
 static audio_format_t audio_format = {
         .format = AUDIO_BUFFER_FORMAT_PCM_S16,
-        .sample_freq = 20000,
+        .sample_freq = 22256, // 60.15Hz*370, rounded up
         .channel_count = 1,
 };