avformat/riffenc: Fix outdated comment

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/riffenc.c

@@ -72,7 +72,7 @@ int ff_put_wav_header(AVFormatContext *s, AVIOContext *pb,
     }
 
     /* We use the known constant frame size for the codec if known, otherwise
-     * fall back on using AVCodecContext.frame_size, which is not as reliable
+     * fall back on using AVCodecParameters.frame_size, which is not as reliable
      * for indicating packet duration. */
     frame_size = av_get_audio_frame_duration2(par, par->block_align);