feat：path问题修复

@@ -37,7 +37,7 @@ class Api
     // 获取K线数据
     public function klines($param)
     {
-        $path = '/api/v2/spot/market/candles';
+        $path = '/api/v2/mix/market/candles';
         $method = 'GET';
         return $this->request($path, $method, $param);
     }
@@ -46,7 +46,7 @@ class Api
     // 下单
     public function placeOrder($param)
     {
-        $path = '/api/v2/spot/trade/place-order';
+        $path = '/api/v2/mix/order/place-order';
         $method = 'POST';
         return $this->request($path, $method, $param, true);
     }
@@ -70,7 +70,7 @@ class Api
     // 查询账户余额
     public function accountBalance($param)
     {
-        $path = '/api/v2/spot/account/assets';
+        $path = '/api/v2/mix/account/account';
         $method = 'GET';
         return $this->request($path, $method, $param, true);
     }