Mention collections which do not support query in websocket subscription documentation

[ebsi-cvalusek]

Describe the Request

I think it would be best to mention the query parameter will be ignored when subscribing to directus_collections and directus_fields.

Specifically, here: https://docs.directus.io/guides/real-time/subscriptions/websockets.html#specifying-fields-to-return

Maintenance Strategy

Only when additional collections do not support query.