pyav 14 breaks unit-tests

[NicolasHug]

pyav 14 was released a few hours ago an CI is red in tests that call write_video():

2024-12-02T11:14:31.5009348Z �[1m�[31mtest/datasets_utils.py�[0m:890: in create_video_file
2024-12-02T11:14:31.5009849Z     torchvision.io.write_video(str(file), video.permute(0, 2, 3, 1), fps, **kwargs)
2024-12-02T11:14:31.5010416Z �[1m�[31mtorchvision/io/video.py�[0m:158: in write_video
2024-12-02T11:14:31.5010777Z     frame.pict_type = "NONE"
2024-12-02T11:14:31.5011269Z �[1m�[31mav/video/frame.pyx�[0m:193: in av.video.frame.VideoFrame.pict_type.__set__
2024-12-02T11:14:31.5011714Z     ???
2024-12-02T11:14:31.5012017Z �[1m�[31mE   TypeError: an integer is required�[0m

https://github.com/pytorch/vision/actions/runs/12117806658/job/33780993942?pr=8601

The change probably comes from this PR PyAV-Org/PyAV@caaddbf