This removes the `add` from op list of stream event, as we do not
actually generate the stream/add event in the API, and when a stream
is created we identify it using the `create` operation.
(This was likely just a mistake introduced as a result of the fact
that `create` does not fit the normal naming scheme; probably
long-term we should actually migrate this to "add", but more important
for now is to document what's accurate).
Part of #17568.