Windows JPEG builds are failing on CI

[fmassa]

🐛 Bug

CI today has been failing with the following error

C:\tools\MINICO~1\CONDA-~2\TORCHV~1\work\torchvision\csrc\io\image\cpu\encode_jpeg.cpp(77): error C2664: 'void jpeg_mem_dest(j_compress_ptr,unsigned char **,size_t *)': cannot convert argument 3 from 'unsigned long *' to 'size_t *'

See https://app.circleci.com/pipelines/github/pytorch/vision/7858/workflows/3f6aa4f8-ba63-48d6-b939-4f97af2e3573/jobs/555947 for one example