avutil/samplefmt: remove outdated comment

av_samples_fill_arrays() has been returning the minimum required buffer size
for a while now.

Signed-off-by: James Almer <jamrial@gmail.com>

libavutil/samplefmt.h

@@ -195,9 +195,8 @@ int av_samples_get_buffer_size(int *linesize, int nb_channels, int nb_samples,
  * @param nb_samples       the number of samples in a single channel
  * @param sample_fmt       the sample format
  * @param align            buffer size alignment (0 = default, 1 = no alignment)
- * @return                 >=0 on success or a negative error code on failure
- * @todo return minimum size in bytes required for the buffer in case
- * of success at the next bump
+ * @return                 minimum size in bytes required for the buffer on success,
+ *                         or a negative error code on failure
  */
 int av_samples_fill_arrays(uint8_t **audio_data, int *linesize,
                            const uint8_t *buf,