avformat/matroskaenc: Fix outdated comment

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

libavformat/matroskaenc.c

@@ -2732,8 +2732,8 @@ static int mkv_check_new_extra_data(AVFormatContext *s, const AVPacket *pkt)
         }
         break;
 #endif
-    // FIXME: Remove the following once libaom starts propagating extradata during init()
-    //        See https://bugs.chromium.org/p/aomedia/issues/detail?id=2012
+    // FIXME: Remove the following once libaom starts propagating proper extradata during init()
+    //        See https://bugs.chromium.org/p/aomedia/issues/detail?id=2208
     case AV_CODEC_ID_AV1:
         if (side_data_size && mkv->track.bc && !par->extradata_size) {
             // If the reserved space doesn't suffice, only write