Remove potentialy insecure Nginx configuration from Kratos "Deploy to production" guide

[BZ1234567890]

Deploy to production guide for Kratos includes instructions for setting up Nginx configuration (relevant section is Install and configure Nginx). These instructions contain the following piece of configuration, which exposes admin APIs to the public without any restrictions:

    location /identities {
                proxy_pass http://admin_api;
                proxy_redirect          off;
                proxy_set_header        Host            $host;
                proxy_set_header        X-Real-IP       $remote_addr;
                proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
    }

I don't see a point of exposing /identities admin route to the public, and I recommend that this piece of code is removed from the deployment guide, unless there is a well documented reason why this should be in the Nginx configuration and how to properly secure admin APIs.

[aeneasr]

Thank you! That should definitely be solved better - would you mind opening a PR how it should be, please? :)