Changes to Get topic message by id and sequence number

the response property _status/messages/items/data became nullable for the status 400

the response property _status/messages/items/data became nullable for the status 404

the response property _status/messages/items/detail became nullable for the status 400

the response property _status/messages/items/detail became nullable for the status 404

the response property chunk_info became nullable for the status 200

the response property chunk_info/initial_transaction_id/account_id became nullable for the status 200

the response property chunk_info/initial_transaction_id/nonce became nullable for the status 200

the response property chunk_info/initial_transaction_id/scheduled became nullable for the status 200

the response property payer_account_id became nullable for the status 200

the response property topic_id became nullable for the status 200