Unable to Access Intel-Optimized PyTorch Packages

[ChristianZaccaria]

We are having some trouble syncing changes and generating a PR in the notebooks repo. After investigating, it seems it's failing to install a requirement in notebooks repo.

Error:
ERROR: Could not install requirement intel-extension-for-pytorch==2.1.100 from [https://intel-extension-for-pytorch.s3.amazonaws.com/ipex_stable/cpu/./intel_extension_for_pytorch-2.1.100%2Bcpu-cp311-cp311-linux_x86_64.whl](https://intel-extension-for-pytorch.s3.amazonaws.com/ipex_stable/cpu/intel_extension_for_pytorch-2.1.100%2Bcpu-cp311-cp311-linux_x86_64.whl) (from -r /tmp/pipenv-ycsirlep-requirements/pipenv-8ax2iss2-constraints.txt (line 40)) because of HTTP error 403 Client Error: Forbidden for url: https://intel-extension-for-pytorch.s3.amazonaws.com/ipex_stable/cpu/intel_extension_for_pytorch-2.1.100%2Bcpu-cp311-cp311-linux_x86_64.whl for URL [https://intel-extension-for-pytorch.s3.amazonaws.com/ipex_stable/cpu/./intel_extension_for_pytorch-2.1.100%2Bcpu-cp311-cp311-linux_x86_64.whl](https://intel-extension-for-pytorch.s3.amazonaws.com/ipex_stable/cpu/intel_extension_for_pytorch-2.1.100%2Bcpu-cp311-cp311-linux_x86_64.whl) (from https://pytorch-extension.intel.com/release-whl/stable/cpu/us/intel-extension-for-pytorch/)

Known Issue: intel/intel-extension-for-pytorch#745

Workaround suggested:
Use cn index url instead on all instances of this throughout the notebooks repo.

[ChristianZaccaria]

cc: @andyatmiami