Document that client.organization is mandatory in connection profile

There is not such thing [in the connection profile ref doc](https://hlf.readthedocs.io/en/latest/developapps/connectionprofile.html). We are only aware of that by walking through your code [here](https://github.com/hyperledger/fabric-sdk-java/blob/87e99f63091db3bc946a2bdfc0c387d985d53e93/src/main/java/org/hyperledger/fabric/sdk/NetworkConfig.java#L243) .