Update AWS docs

Author: hwdsl2

aws/README-zh.md

@@ -9,7 +9,7 @@
 可用的自定义参数：
 
 - Amazon EC2 实例类型
-> **注：** 在任意 AWS 区域中，某些此模版提供的实例类型可能不可用。比如说 `m5a.large` 可能无法在 `ap-east-1` 区域部署。（仅为假设）在其情况下，您会在部署过程中遇到此错误：`The requested configuration is currently not supported. Please check the documentation for supported configurations`. 新建成的 AWS 区域更容易造成此问题，因为这些新区域提供的实例类型不是很多。
+> **注：** 在某些 AWS 区域中，此模版提供的某些实例类型可能不可用。比如 `m5a.large` 可能无法在 `ap-east-1` 区域部署（仅为假设）。在此情况下，你会在部署过程中遇到此错误：`The requested configuration is currently not supported. Please check the documentation for supported configurations`。新开放的 AWS 区域更容易出现此问题，因为它们提供的实例类型较少。
 - VPN 服务器的操作系统（Ubuntu 20.04/18.04/16.04，Debian 9）
 > **注：** 在 EC2 上使用 Debian 9 映像之前，你需要先在 AWS Marketplace 上订阅：[Debian 9](https://aws.amazon.com/marketplace/pp/B073HW9SP3)。
 - 你的 VPN 用户名

aws/README.md

@@ -9,7 +9,7 @@ This template will create a fully-working IPsec VPN server on Amazon Elastic Com
 Available customization parameters:
 
 - Amazon EC2 instance type
-> **Note**: The instance type options offered by this template are possibly not **ALL** available in any specific region. For example, you may not be able to deploy a `m5a.large` instance in ap-east-1.(hypothetically) In that case, you might experience the following error during deployment: `The requested configuration is currently not supported. Please check the documentation for supported configurations`. Newly released regions are prone to causing that problem as there is less variaty of instances.
+> **Note**: It is possible that not all instance type options offered by this template are available in a specific AWS region. For example, you may not be able to deploy an `m5a.large` instance in `ap-east-1` (hypothetically). In that case, you might experience the following error during deployment: `The requested configuration is currently not supported. Please check the documentation for supported configurations`. Newly released regions are more prone to having this problem as there are less variety of instances.
 - OS for your VPN server (Ubuntu 20.04/18.04/16.04, Debian 9)
 > **Note:** Before using the Debian 9 image on EC2, you need to first subscribe at the AWS Marketplace: [Debian 9](https://aws.amazon.com/marketplace/pp/B073HW9SP3).
 - Your VPN username