lavr: correct the documentation for the ff_audio_resample() return value

libavresample/resample.h

@@ -62,7 +62,7 @@ void ff_audio_resample_free(ResampleContext **c);
  * @param dst       destination audio data
  * @param src       source audio data
  * @param consumed  number of samples consumed from the source
- * @return          number of samples written to the destination
+ * @return          0 on success, negative AVERROR code on failure
  */
 int ff_audio_resample(ResampleContext *c, AudioData *dst, AudioData *src,
                       int *consumed);