[Bug]: workshop Terraform EKS config uses pre-v21 module arguments with terraform-aws-modules/eks/aws v21.0.9

### Installation method

Own AWS account

### What happened?

## Summary

The Terraform in `environment/terraform/eks.tf` is pinned to `terraform-aws-modules/eks/aws` `21.0.9`, but the module block uses older argument names that are not valid in v21.

## Files

- `environment/terraform/eks.tf`
- `environment/terraform/variables.tf`

## Actual result
Terraform fails with errors like:
An argument named "cluster_name" is not expected here.
An argument named "cluster_version" is not expected here.
An argument named "cluster_addons" is not expected here.
An argument named "cluster_remote_network_config" is not expected here.

### What did you expect to happen?

## Expected result
The tutorial and repo should be internally consistent so terraform apply works without manual translation of module arguments.

### How can we reproduce it?

From `environment/terraform`:

```bash
terraform apply -var="cluster_name=$EKS_CLUSTER_NAME" -auto-approve
```

### Anything else we need to know?

_No response_

### EKS version

1.33

Start in environment/terraform/eks.tf and environment/terraform/variables.tf, then run terraform apply -var="cluster_name=$EKS_CLUSTER_NAME" -auto-approve from environment/terraform to reproduce the v21.0.9 argument errors. Compare the module block with the v21 argument names and verify that the tutorial configuration applies without manual translation.

Written by the indexing model from the issue text.