avcodec/dxv: remove code that is never reached

The function is automatically called.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/dxv.c

@@ -397,8 +397,6 @@ static int dxv_decode(AVCodecContext *avctx, void *data,
     ret = ff_thread_get_buffer(avctx, &tframe, 0);
     if (ret < 0)
         return ret;
-    if (avctx->codec->update_thread_context)
-        ff_thread_finish_setup(avctx);
 
     /* Now decompress the texture with the standard functions. */
     avctx->execute2(avctx, decompress_texture_thread,