Croissant 1.1 uses "@vocab": "http://schema.org/" (non-HTTPS)

[pdurbin]

See this PR:

• 1.1 chore: Verify and fix link urls mlcommons/croissant#929

"For namespace URLs, we use http:// (that's an issue discussed at length in the schema.org community, and you can probably find an older issue about it.)" -- mlcommons/croissant#929 (review)

This is a change from Croissant 1.0 which used "@vocab": "http://schema.org/" (HTTPS).