m.fully_read example is misleading

[zecakeh]

Link to problem area: https://matrix.org/docs/spec/client_server/r0.6.1#m-fully-read

Issue
The example in this area is misleading because it shows the event with a room_id key, but it should never be received like that because in the sync response it's received inside a Joined Room > Account Data object, and if you call the room account data endpoint you only receive the content.

Expected behaviour
This should be the example provided, similar to m.tag, as one would receive it in the sync response:

{
    "content": {
        "event_id": "$someplace:example.org"
    },
    "type": "m.fully_read"
}