Collection JSON-LD frame: "False" should be false

In https://www.w3.org/TR/annotation-vocab/#annotation-collection-frame

```json
  "first": [{"@embed": "False"}],
  "last": [{"@embed": "False"}]
```

should be

```json
  "first": [{"@embed": false}],
  "last": [{"@embed": false}]
```