fix: invalid signature cause by 0x + signature.hex()

Author: 1yam

src/aleph/sdk/chains/common.py

@@ -72,7 +72,7 @@ async def sign_message(self, message: Dict) -> Dict:
         """
         message = self._setup_sender(message)
         signature = await self.sign_raw(get_verification_buffer(message))
-        message["signature"] = "0x" + signature.hex()
+        message["signature"] = signature.hex()
         return message
 
     @abstractmethod