Update declarations for vocabulary consistency

[Ndpnt]

Currently, in services declarations terms are declared in a key named documents.
For vocabulary consistency, this should now be named terms, like that:

{
  "name": "Open Terms Archive",
  "terms": {
    "Privacy Policy": {
      "fetch": "https://opentermsarchive.org/fr/privacy-policy",
      "select": ".TextContent_textContent__ToW2S"
    },
    "Imprint": {
      "fetch": "https://opentermsarchive.org/fr/legal-notice",
      "select": ".TextContent_textContent__ToW2S"
    }
  }
}