Label example in Section 6.1

[Daniel Fett]

The first example in Section 6.1 shows a credential, not a type metadata document, but is not labelled as such.

The example in question:

{
  "vct": "https://betelgeuse.example.com/education_credential",
  "vct#integrity": "sha256-WRL5ca_xGgX3c1VLmXfh-9cLlJNXN-TsMk-PmKjZ5t0",
  ...
}