lavf/concatdec: remove unrelated change during codecpar merge.

Clearing the extradata is not related to the codecpar change,
and it breaks if auto_convert is disabled.

Fix trac ticket #5461.

libavformat/concatdec.c

@@ -182,11 +182,6 @@ static int copy_stream_props(AVStream *st, AVStream *source_st)
     }
     if ((ret = avcodec_parameters_copy(st->codecpar, source_st->codecpar)) < 0)
         return ret;
-    /* We don't want to carry around MP4-style extradata, since we are usoign a bsf anyway. */
-    if (st->codecpar->codec_id == AV_CODEC_ID_H264) {
-        av_freep(&st->codecpar->extradata);
-        st->codecpar->extradata_size = 0;
-    }
     st->r_frame_rate        = source_st->r_frame_rate;
     st->avg_frame_rate      = source_st->avg_frame_rate;
     st->time_base           = source_st->time_base;