apigw-data-validation-tf: Update AWS provider and remove duplicate body validation resource

[bentsku]

Issue #, if available:

Description of changes:
While trying to deploy the apigw-data-validation-tf sample, I've noticed that the Lambda Runtime has been updated to Python 3.13, but the Terraform AWS provider has been pinned to the 4.x version. Python 3.13 is not a valid value for this older runtime, and this makes Terraform reject and fail. I've updated it to 5.x.

It also did not deploy because the Model resource was declared both in the OpenAPI body of the REST API as well as its own Terraform resource, leading to an exception:

╷
│ Error: creating API Gateway Model (Vehicle): operation error API Gateway: CreateModel, https response error StatusCode: 409, RequestID: c2af2518-04d1-4455-baf7-b53fc718c8ac, ConflictException: Model name already exists for this REST API
│ 
│   with aws_api_gateway_model.vehicle_model,
│   on main.tf line 142, in resource "aws_api_gateway_model" "vehicle_model":
│  142: resource "aws_api_gateway_model" "vehicle_model" {
│ 
╵

So I've deleted the OpenAPI body to make sure the Model was declared in Terraform and could be accessed in the aws_api_gateway_method.

The sample now deploys correctly against AWS.

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[ellisms]

Hi @bentsku Thanks for catching this and supplying the fix. I validated this works as expected and will add to the publishing queue.