chore: bump Terraform 1.15.1 -> 1.15.4

[NWarila]

Summary

Bumps terraform/versions.tf required_version = "= 1.15.4" and the docs reference. Aligns this org framework with the consumer bumps in NWarila/github-terraform-runner and NWarila/terraform-runner-template so consumer terraform init with 1.15.4 satisfies the framework's exact-pin constraint.

Test plan

• CI green

[github-actions]

Terraform Framework Test Results

Check	Status
Format	✅
Init	✅
Validate	✅
Test Suite	✅

Runs: 55 total, 55 passed, 0 failed, 0 skipped

Full test output

tests/normalization.tftest.hcl... in progress
  run "pattern_blocks_with_only_pattern_field_plans_clean"... pass
  run "merge_queue_with_partial_fields_plans_clean"... pass
  run "pull_request_with_only_merge_methods_plans_clean"... pass
  run "pages_partial_fields_plans_clean"... pass
  run "repo_with_environments_plans_clean"... pass
  run "archived_repo_plans_clean"... pass
  run "empty_repo_set_plans_clean"... pass
  run "org_mode_explicit_codeowners_plans_clean"... pass
  run "personal_mode_synthesizes_codeowners"... pass
  run "push_ruleset_on_private_when_supported_plans_clean"... pass
  run "license_template_defaults_null_not_MIT"... pass
  run "good_minimal_produces_expected_resource_counts"... pass
  run "good_minimal_carries_expected_defaults"... pass
  run "archived_repo_filters_out_downstream_locals"... pass
  run "empty_repo_set_exercises_every_filter_on_zero_input"... pass
  run "good_minimal_produces_zero_environments_zero_codeowners"... pass
  run "explicit_security_and_analysis_overrides_baseline"... pass
  run "multi_branch_sources_all_from_default_not_serially"... pass
  run "fork_repo_passes_through_source_fields"... pass
tests/normalization.tftest.hcl... tearing down
tests/normalization.tftest.hcl... pass
tests/preconditions.tftest.hcl... in progress
  run "rejects_invalid_visibility_enum"... pass
  run "rejects_public_repo_without_description"... pass
  run "rejects_invalid_ruleset_enforcement"... pass
  run "rejects_org_mode_codeowners_required_but_missing"... pass
  run "rejects_env_wait_timer_out_of_range"... pass
  run "rejects_env_branch_policy_mutually_exclusive"... pass
  run "rejects_actions_allowed_actions_enum"... pass
  run "rejects_actions_selected_without_config"... pass
tests/preconditions.tftest.hcl... tearing down
tests/preconditions.tftest.hcl... pass
tests/security.tftest.hcl... in progress
  run "strict_mode_no_gap_plans_clean"... pass
  run "compatibility_mode_no_gap_plans_clean_with_empty_preview"... pass
  run "strict_mode_reports_gaps_across_multiple_visibilities"... pass
  run "no_baseline_no_yaml_collapses_security_to_null"... pass
  run "baseline_feature_enabled_when_capability_matches"... pass
tests/security.tftest.hcl... tearing down
tests/security.tftest.hcl... pass
tests/validation.tftest.hcl... in progress
  run "good_minimal_plans_clean"... pass
  run "rejects_unknown_top_level_key"... pass
  run "rejects_unknown_nested_key"... pass
  run "rejects_allow_forking"... pass
  run "rejects_duplicate_repo_keys"... pass
  run "rejects_unsupported_push_ruleset"... pass
  run "rejects_code_scanning_tool_typo"... pass
  run "rejects_multiple_nested_typos_in_one_repo"... pass
  run "rejects_secrets_written_as_map"... pass
  run "rejects_token_mode_missing_token"... pass
  run "rejects_app_mode_missing_app_auth"... pass
  run "rejects_token_mode_with_app_auth_also_set"... pass
  run "rejects_app_mode_with_token_also_set"... pass
  run "valid_app_auth_plans_clean"... pass
  run "strict_mode_fails_on_capability_gap"... pass
  run "compatibility_mode_tolerates_capability_gap"... pass
  run "push_ruleset_public_supports_true_still_fails"... pass
  run "push_ruleset_private_supports_false_fails"... pass
  run "push_ruleset_internal_supports_true_passes"... pass
  run "push_ruleset_internal_supports_false_fails"... pass
  run "rejects_invalid_github_owner_regex"... pass
  run "rejects_invalid_auth_mode_enum"... pass
  run "rejects_invalid_baseline_mode_enum"... pass
tests/validation.tftest.hcl... tearing down
tests/validation.tftest.hcl... pass

Success! 55 passed, 0 failed.

Commit: 0b01141