waf-apigw-rest: Update runtime to python3.13

[kakakakakku]

Issue #, if available:
N/A

Description of changes:
Hi😀 Thanks for the useful patterns!

To prevent future deployment issues, I updated the Lambda runtime python3.9 to python3.13.
The python3.9 runtime is scheduled to be deprecated in December.
See https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html

Check

sam deploy completed successfully and works good.

By the way, since I live in Japan, I checked by setting the CountryCodes in the GeoMatchStatement to JP.

$ curl -s https://2uhf34riq6.execute-api.ap-northeast-1.amazonaws.com/Prod | jq .
{
  "message": "Request received by Lambda function"
}

Thank you😀

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.