Fix build with ffmpeg 6.0 (#8096)

Signed-off-by: Zoltán Böszörményi <zboszor@gmail.com>
Co-authored-by: Nicolas Hug <nh.nicolas.hug@gmail.com>

torchvision/csrc/io/decoder/stream.cpp

@@ -63,16 +63,9 @@ int Stream::openCodec(std::vector<DecoderMetadata>* metadata, int num_threads) {
     codecCtx_->thread_count = num_threads;
   } else {
     // otherwise set sensible defaults
-    // with the special case for the different MPEG4 codecs
-    // that don't have threading context functions
-    if (codecCtx_->codec->capabilities & AV_CODEC_CAP_INTRA_ONLY) {
-      codecCtx_->thread_type = FF_THREAD_FRAME;
-      codecCtx_->thread_count = 2;
-    } else {
     codecCtx_->thread_count = 8;
     codecCtx_->thread_type = FF_THREAD_SLICE;
   }
-  }
 
   int ret;
   // Copy codec parameters from input stream to output codec context