Feature Request: Provide a sample CloudFront function example for changing custom origins

Hello, I'm submitting this feedback on behalf of an AWS Premium Support customer who referenced https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/example_cloudfront_functions_select_origin_based_on_country_section.html for using CloudFront Function's new origin modification feature. It wasn't clear that the `"originAccessControlConfig": {...}` structure should be removed when using custom origins.

There is more information in https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/helper-functions-origin-modification.html that addresses this confusion.

It may be helpful to also have a function example that demonstrates rerouting the origin for custom origins.