Generate sphinx docs with secure content. (#18508)

Generate sphinx docs with secure content. (#18508)

Summary:
There are a number of pages in the docs that serve insecure content. AFAICT this is the sole source of that.

I wasn't sure if docs get regenerated for old versions as part of the automation, or if those would need to be manually done.

cf. https://github.com/pytorch/pytorch.github.io/pull/177
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18508

Differential Revision: D14645665

Pulled By: zpao

fbshipit-source-id: 003563b06048485d4f539feb1675fc80bab47c1b