Invalid region: ap-southeast-4

When using `amazon-ebs` and setting `ami_regions` it fails when specifying `ap-southeast-4`.

```
Build 'amazon-ebs.image_arm64' errored after 1 second 770 milliseconds: error validating regions: Invalid region(s): [ap-southeast-4], available regions: [ap-south-1 eu-north-1 eu-west-3 eu-west-2 eu-west-1 ap-northeast-3 ap-northeast-2 ap-northeast-1 ca-central-1 sa-east-1 ap-southeast-1 ap-southeast-2 eu-central-1 us-east-1 us-east-2 us-west-1 us-west-2]
```

Packer v1.15.0
Plugin v1.8.0