Update AWS docs

- Add a note on cleaning up the key pair(s)

aws/README-zh.md

@@ -34,6 +34,8 @@
 
 要指定一个 AWS 区域，你可以使用导航栏上你的帐户信息右侧的选择器。当你在最后一步中点击 "create stack" 之后，请等待堆栈创建和 VPN 安装完成，可能需要最多 15 分钟。一旦堆栈的部署状态变成 **"CREATE_COMPLETE"** ，你就可以连接到 VPN 服务器了。单击 **Outputs** 选项卡以查看你的 VPN 登录信息，然后继续下一步：[配置 VPN 客户端](../README-zh.md#下一步)。
 
+> **注**：如果你删除使用此模板部署的 CloudFormation 堆栈，在部署期间添加的密钥对将不会自动被清理。要管理你的密钥对，请转到 EC2 控制台 -> 密钥对。
+
 ## 常见问题
 
 <details>

aws/README.md

@@ -34,6 +34,8 @@ Click the icon below to start:
 
 You may choose an AWS region using the selector to the right of your account information on the navigation bar. After you click "create stack" in the final step, please wait for the stack creation and VPN setup to complete, which may take up to 15 minutes. As soon as the stack's status changes to **"CREATE_COMPLETE"**, you are ready to connect to the VPN server. Click the **Outputs** tab to view your VPN login details. Then continue to [Next steps: Configure VPN Clients](../README.md#next-steps).
 
+> **Note**: If you delete a CloudFormation stack deployed using this template, the key pair that was added during deployment won't be automatically cleaned up. To manage your key pairs, go to EC2 console -> Key Pairs.
+
 ## FAQs
 
 <details>