Quickstart: region mixin

### Describe the Bug

The quickstart provides an exampe for the vpc component with region mixin.
When generating the vars, the vars from the region mixin are not included.

### Expected Behavior

region vars included

### Steps to Reproduce

Follow the quickstart

### Screenshots

https://github.com/cloudposse/atmos/blob/9fe34c098385ae8f44f3223beed94b5fb3ed5210/website/docs/quick-start/create-atmos-stacks.md?plain=1#L207-L225

https://github.com/cloudposse/atmos/blob/9fe34c098385ae8f44f3223beed94b5fb3ed5210/website/docs/quick-start/create-atmos-stacks.md?plain=1#L314-L351

### Environment

_No response_

### Additional Context

When changing the "vpc" in the regions mixin to "vpc-1", the vars from the region mixin are included in the generated vars.