peer: use MaxMessagePayload instead of hard coding

lnwire/error.go

@@ -124,7 +124,7 @@ func (c *Error) MsgType() MessageType {
 // This is part of the lnwire.Message interface.
 func (c *Error) MaxPayloadLength(uint32) uint32 {
 	// 32 + 2 + 65501
-	return 65535
+	return MaxMessagePayload
 }
 
 // isASCII is a helper method that checks whether all bytes in `data` would be