remove useless code, found by oded

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@10066 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/nutenc.c

@@ -498,7 +498,6 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt){
 
         if(flags & FLAG_CODED){
             length++;
-            flags &= ~needed_flags;
             flags |=  needed_flags;
         }