Clarify streaming support with apigateway-v2

[dacevedo12]

AWS only recently announced streaming support for apigateway v1 (REST) https://aws.amazon.com/blogs/compute/building-responsive-apis-with-amazon-api-gateway-response-streaming/ but it still does not apply to apigateway v2 (HTTP).

If one attempts to set

    override: {
      converter: "aws-apigw-v2",
      wrapper: "aws-lambda-streaming",
    },

It will return 500

The following matrix and docs are misleading then

opennextjs-aws/packages/open-next/src/build/validateConfig.ts

Line 19 in 4255fb7

"aws-lambda-streaming": ["aws-apigw-v2"],

https://github.com/opennextjs/docs/blob/8a7044b67f462fc3f4da036ad0ac55f00e7c456b/pages/aws/config/full_example.mdx?plain=1#L16