Fix gate.io fetchOrders
Fix gate.io fetchOrders

This is what `response` is for me from gate.io at this point:

```
{'result': 'true', 'orders': [], 'message': 'Success', 'code': 0, 'elapsed': '0.892ms'}
```
ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt