fair.pkg.atmeta.com serving expired TLS certificate — breaks pip install

The package index at https://fair.pkg.atmeta.com/fairseq2/whl/ (referenced in the
README's "Variants" install instructions) is currently serving an expired TLS
certificate:

SSLCertVerificationError: certificate has expired

Reproduced two ways:
1. `pip install fairseq2 --extra-index-url https://fair.pkg.atmeta.com/fairseq2/whl/pt2.8.0/cpu`
fails to fetch several transitive nvidia-* wheels from that host.
2. Fetching https://fair.pkg.atmeta.com/fairseq2/whl/pt2.8.0/cpu/ directly in a
browser / HTTP client also fails with the same certificate error.

This blocks anyone following the documented install instructions for a specific
torch/CUDA variant. Could someone on the infra side renew the cert?

Start with the README's “Variants” install instructions and reproduce the failure using the documented pip command or by fetching the fair.pkg.atmeta.com URL directly. Done means the package index presents a valid TLS certificate and the documented variant installation can fetch its wheels without certificate errors.

Written by the indexing model from the issue text.