terraform lockfile to s3 use_lockfile from dynamodb_table

[here]

Terraform 1.11+ supports native S3 lockfile locking, making the DynamoDB-based lock table deprecated. Both prod.backend.tfvars and backend.tf currently print a Deprecated Parameter warning on every plan/apply run.

Refs hackforla/devops#218

What changes did you make?

• Delete the dynamodb_table = "hfla_incubator_terraform_table" line and add use_lockfile = true.
• Add a no-op comment line to any .tf file in the same PR.

Why did you make the changes (we will use this info to test)?

• Follow testing in Migrate the Terraform S3 backends off dynamodb_table onto use_lockfile and delete the lock tables devops#218 to confirm plan and apply run as expected
• Treat a non-empty plan as a hard gate.
• After the PR merges, confirm the Terraform apply (OIDC) run succeeds and that no Deprecated Parameter warning appears anywhere in its log.

[github-actions]

Terraform plan in terraform
With backend config files: terraform/prod.backend.tfvars

No changes. Your infrastructure matches the configuration.

No changes. Your infrastructure matches the configuration.

Terraform has compared your real infrastructure against your configuration
and found no differences, so no changes are needed.

✅ Plan applied in Terraform apply (OIDC) #98