Update SubClientLoginSerializer_v291.java

[terryherbert]

After investigating why Spilt Screen functionality was not functioning on GeyserMC, I discovered that the SubClientLogin message received from the Bedrock client could not be deserialize by SubClientLoginSerializer_v291.

The original code expected a JSONArray off the wire, however we were actually getting a JSONObject containing JSONArray when you get "chain".

Further investigation I discovered that this mirrors precisely what the LoginSerializer_v291, the only exception is that SubClientLogin message does not start with the protocol version.

I have updated the serialize method to mirror that of deserialize.

With these changes plus a some additional in GeyserMC works.