v210enc: remove redundant assignment

Signed-off-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/v210enc.c

@@ -44,7 +44,6 @@ static av_cold int encode_init(AVCodecContext *avctx)
     if (!avctx->coded_frame)
         return AVERROR(ENOMEM);
 
-    avctx->coded_frame->key_frame = 1;
     avctx->coded_frame->pict_type = AV_PICTURE_TYPE_I;
 
     return 0;