Update schema in demo code with latest standard specification

[sondreb]

This schema/context document defines "publicKey", which I don't think is part of the did-document specification any longer?

https://github.com/transmute-industries/vc.js/blob/master/packages/web-app-smoke-tester/src/did-doc.json

[OR13]

thanks for reporting this... our smoke tests and fixtures in the repo need a lot of cleanup.

[OR13]

publicKey was replace with verificationMethod.