avcodec: remove warning against using frame threading with hwaccels

libavcodec now automatically serializes decoding for hwaccels which
are not thread-safe. This means API users, which rely on the libavcodec
native software fallback mechanism, can now simply enable threading
without running into problems.

libavcodec/utils.c

@@ -1076,11 +1076,6 @@ static int setup_hwaccel(AVCodecContext *avctx,
     AVHWAccel *hwa = find_hwaccel(avctx->codec_id, fmt);
     int ret        = 0;
 
-    if (avctx->active_thread_type & FF_THREAD_FRAME) {
-        av_log(avctx, AV_LOG_WARNING,
-               "Hardware accelerated decoding with frame threading is known to be unstable and its use is discouraged.\n");
-    }
-
     if (!hwa) {
         av_log(avctx, AV_LOG_ERROR,
                "Could not find an AVHWAccel for the pixel format: %s",