fix: make specification align with the current SDKs state

[ttypic]

For publish, for example, we treat INITIALIZED as a state where messages can be queued (sent later after we connected):

(RTL6c2) If the connection is INITIALIZED, CONNECTING or DISCONNECTED; and the channel is neither SUSPENDED nor FAILED; and ClientOptions#queueMessages is true; then the message will be placed in a connection-wide message queue to be delivered as soon as the connection is CONNECTED.

However, for attach, it’s different:

(RTL4b) If the connection state is INITIALIZED, CLOSED, CLOSING, SUSPENDED or FAILED, the attach request results in an error

In every SDK I checked (ably-js, ably-java, ably-ruby, ably-cocoa) we don’t follow this, we don’t fail if connection state is INITIALIZED , channel state transitions to attaching.