avisynth: Remove wrong pts calculation.

Fixes Ticket428
(cherry picked from commit 4f123a7d7c)

libavformat/avisynth.c

@@ -165,7 +165,6 @@ static int avisynth_read_packet(AVFormatContext *s, AVPacket *pkt)
 
   res = AVIStreamRead(stream->handle, stream->read, stream->chunck_samples, pkt->data, stream->chunck_size, &read_size, NULL);
 
-  pkt->pts = stream->read;
   pkt->size = read_size;
 
   stream->read += stream->chunck_samples;