Add link.prefetch attribute data for secure contexts required (#3397)
Add link.prefetch attribute data for secure contexts required (#3397)

* prefetch attribute is only supported on secure contexts.

* Update html/elements/link.json

Co-Authored-By: jpmedley <e5f32d9ca37888f2e401c8370536acae62d3b209@google.com>

* Update html/elements/link.json

Co-Authored-By: jpmedley <e5f32d9ca37888f2e401c8370536acae62d3b209@google.com>

chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,mdn/browser-compat-data