avformat/matroskaenc: Remove outdated comment

This comment does not account for the fact that the limits on cluster
size and duration are configurable by the user since 98308bd4.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/matroskaenc.c

@@ -2454,8 +2454,6 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
         cluster_time = pkt->pts - mkv->cluster_pts;
     cluster_time += mkv->tracks[pkt->stream_index].ts_offset;
 
-    // start a new cluster every 5 MB or 5 sec, or 32k / 1 sec for streaming or
-    // after 4k and on a keyframe
     cluster_size = avio_tell(mkv->cluster_bc);
 
     if (mkv->is_dash && codec_type == AVMEDIA_TYPE_VIDEO) {