fix: raw message encoding in TransferTransaction

[OlegMakarenko]

Problem

The message is not correctly encoded when creating a TransferTransaction with RawMessage.
The Uint8Array is encoded to a hex string during RawMessage.create().
Then in the getMessageBuffer() of TransferTransaction the hex string (considered as a plain utf-8 text string) is converted to hex string again.
Also, an extra 0xFF byte is added at the beginning of the raw message.

Solution

• Remove double conversion of RawMessage.payload to hex in TransferTransaction.getMessageBuffer(), since the payload is already in hex.
• Remove adding an extra byte to the beginning of the message.

[Jaguar0625]

👍