avformat/segment: Don't set extradata size twice

ff_alloc_extradata() already sets the size of the extradata so doing it
again is unnecessary.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Reviewed-by: Gyan Doshi <ffmpeg@gyani.pro>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/segment.c

@@ -882,7 +882,6 @@ static int seg_write_packet(AVFormatContext *s, AVPacket *pkt)
                 goto calc_times;
             }
             memcpy(st->codecpar->extradata, pkt_extradata, pkt_extradata_size);
-            st->codecpar->extradata_size = pkt_extradata_size;
         }
     }