AWS "host_set_ids" is not expected here

When use AWS terraform, get error:
```
│ Error: Unsupported argument
│
│ on boundary/targets.tf line 8, in resource "boundary_target" "backend_servers_ssh":
│ 8: host_set_ids = [
│
│ An argument named "host_set_ids" is not expected here.
```

Start at boundary/targets.tf line 8 and inspect the boundary_target resource configuration against the AWS Terraform provider schema. Run Terraform validation or planning to reproduce the unsupported-argument error, then confirm the target configuration is accepted without losing the intended backend SSH host-set behavior.

Written by the indexing model from the issue text.