Update env var setting instructions in AWS Gem test README (#4791)

Signed-off-by: Stanko <stankoa@amazon.com>

AutomatedTesting/Gem/PythonTests/AWS/README.md

@@ -9,10 +9,13 @@
 1. Go to the AWS IAM console and create an IAM role called o3de-automation-tests which adds your own account as as a trusted entity and uses the "AdministratorAccess" permissions policy.
 2. Copy {engine_root}\scripts\build\Platform\Windows\deploy_cdk_applications.cmd to your engine root folder.
 3. Open a new Command Prompt window at the engine root and set the following environment variables:
+```
    Set O3DE_AWS_PROJECT_NAME=AWSAUTO
    Set O3DE_AWS_DEPLOY_REGION=us-east-1
+   Set O3DE_AWS_DEPLOY_ACCOUNT={your_aws_account_id}
    Set ASSUME_ROLE_ARN=arn:aws:iam::{your_aws_account_id}:role/o3de-automation-tests
    Set COMMIT_ID=HEAD
+```
 4. In the same Command Prompt window, Deploy the CDK applications for AWS gems by running deploy_cdk_applications.cmd.
    
 ## Run Automation Tests