update documents for vpc egress gateway (#233)

Signed-off-by: zhangzujian <zhangzujian.7@gmail.com>

Author: zhangzujian

docs/advance/vpc-egress-gateway.en.md

@@ -174,8 +174,8 @@ Routing Policies
 If you need to enable load balancing, modify `.spec.replicas` as shown in the following example:
 
 ```shell
-$ kubectl patch veg gateway1 --type=merge -p '{"spec": {"replicas": 2}}'
-vpcegressgateway.kubeovn.io/gateway1 patched
+$ kubectl scale veg gateway1 --replicas=2
+vpcegressgateway.kubeovn.io/gateway1 scaled
 
 $ kubectl get veg gateway1
 NAME       VPC           REPLICAS   BFD ENABLED   EXTERNAL SUBNET   PHASE       READY   AGE

docs/advance/vpc-egress-gateway.md

@@ -174,8 +174,8 @@ Routing Policies
 如果您需要开启多副本负载均衡，修改 `.spec.replicas` 即可，示例如下：
 
 ```shell
-$ kubectl patch veg gateway1 --type=merge -p '{"spec": {"replicas": 2}}'
-vpcegressgateway.kubeovn.io/gateway1 patched
+$ kubectl scale veg gateway1 --replicas=2
+vpcegressgateway.kubeovn.io/gateway1 scaled
 
 $ kubectl get veg gateway1
 NAME       VPC           REPLICAS   BFD ENABLED   EXTERNAL SUBNET   PHASE       READY   AGE

docs/reference/feature-stage.en.md

@@ -78,3 +78,4 @@ This list records the feature stages from the 1.8 release.
 | Load Balance in Custom VPC                       | false   | Alpha | 1.11  |       |
 | DNS in Custom VPC                                | false   | Alpha | 1.11  |       |
 | Underlay and Overlay Interconnection             | false   | Beta  | 1.12  |       |
+| VPC Egress Gateway                               | true    | Alpha | 1.14  |       |

docs/reference/feature-stage.md

@@ -77,3 +77,4 @@
 | [默认 VPC Load Balancer 类型 Service](../guide/loadbalancer-service.md) | false | Alpha | 1.11      |           |
 | [自定义 VPC 内部 DNS](../advance/vpc-internal-dns.md) | false | Alpha | 1.11      |           |
 | [Underlay 和 Overlay 互通](../start/underlay.md) | false | Beta | 1.12      |           |
+| [VPC Egress Gateway](../advance/vpc-egress-gateway.md) | true | Alpha | 1.14      |           |