h264: remove a now redundant error check

It was only relevant when data partitioning was in use.

libavcodec/h264_slice.c

@@ -2338,12 +2338,6 @@ int ff_h264_execute_decode_slices(H264Context *h, unsigned context_count)
     H264Context *hx;
     int i;
 
-    if (h->mb_y >= h->mb_height) {
-        av_log(h->avctx, AV_LOG_ERROR,
-               "Input contains more MB rows than the frame height.\n");
-        return AVERROR_INVALIDDATA;
-    }
-
     if (h->avctx->hwaccel)
         return 0;
     if (context_count == 1) {