Add AWS_REGION to credential requirements

Updated authentication requirements for AWS credentials.

Author: jordanstephens

docs/tutorials/deploy-to-aws.mdx

@@ -26,7 +26,7 @@ $ cd path/to/your/project
 There are many ways to authenticate your [AWS account](https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-authentication.html).
 Once you've done that, Defang will look for your AWS credentials in your shell environment and expect to find one of the following credential sets:
 * the `AWS_PROFILE` environment variable
-* or, the `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` environment variables
+* or, the `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, and `AWS_REGION` environment variables
 
 :::tip
 If you have the AWS CLI installed (which is not required in order to use the Defang CLI), you can verify that you've authenticated to AWS by running `aws sts get-caller-identity` and see your account ID.