Union docs still refer to the old data function

[robotlolita]

E.g. from https://folktale.origamitower.com/api/v2.3.0/en/folktale.adt.union.union.union.html#reflection

Note that if two unions have the same type ID, they'll be considered equivalent by hasInstance. You may pass an object (like Symbol('type name')) to data to avoid this, however reference equality does not work across realms in JavaScript.