avcodec/mpegvideo_dec: Remove commented-out cruft

This piece of code has been added in an already commented-out state
in commit 158c7f059c. It certainly
doesn't make sense now (if ever) because new_picture_ptr it used
has been removed in 6571e41dcd
(and new_picture is only used for encoding).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/mpegvideo_dec.c

@@ -350,8 +350,6 @@ int ff_mpv_frame_start(MpegEncContext *s, AVCodecContext *avctx)
     s->current_picture_ptr->field_picture      =  s->picture_structure != PICT_FRAME;
 
     s->current_picture_ptr->f->pict_type = s->pict_type;
-    // if (s->avctx->flags && AV_CODEC_FLAG_QSCALE)
-    //     s->current_picture_ptr->quality = s->new_picture_ptr->quality;
     s->current_picture_ptr->f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
 
     if ((ret = ff_mpeg_ref_picture(s->avctx, &s->current_picture,