Include a note on reliability of statusOf function

[smol-ninja]

The return value of statusOf cannot be relied upon. It can be manipulated by a smart sender. Take the following example:

1. A call to statusOf is made inside a transaction.
2. The sender sees the pending tx and front runs it by pausing the stream.
3. The function returns PAUSED.
4. The sender sends another tx in the next block to resume the stream.

Therefore, the natspecs of statusOf should mention a note about it as the following:

/// Since Flow offers flexibility to the senders, a sender can pause and resume a stream at any time. Therefore, 
/// it is not recommended to rely solely on the return value of `statusOf`.