Update audio.h (#55)

Fixed comment on audio format.

Author: martindevans

src/common/pico_audio/include/pico/audio.h

@@ -41,7 +41,7 @@ extern "C" {
 #define AUDIO_BUFFER_FORMAT_PCM_S16 1          ///< signed 16bit PCM
 #define AUDIO_BUFFER_FORMAT_PCM_S8 2           ///< signed 8bit PCM
 #define AUDIO_BUFFER_FORMAT_PCM_U16 3          ///< unsigned 16bit PCM
-#define AUDIO_BUFFER_FORMAT_PCM_U8 4           ///< unsigned 16bit PCM
+#define AUDIO_BUFFER_FORMAT_PCM_U8 4           ///< unsigned 8bit PCM
 
 /** \brief Audio format definition
  */