Update aws nlb manifests installation

[bjee19]

There is no longer an aws-nlb deploy.yaml file, so we need to update the manifests installation and give some information on setting annotations in the Gateway.

Problem: There is no longer an aws-nlb deploy.yaml file, so we need to update documentation.

Solution: Update the documentation and give information on setting annotations on the Gateway.

Testing: Checked with make watch

Related with: nginx/nginx-gateway-fabric#3362

Closes

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[sjberman]

Didn't see this PR until it's too late.

I'd update this to show the Gateway spec and the infrastructure labels field so it's very clear where to set these labels. "infrastructure fields" may not be understood.