An empty list of ports does not suffice to disable HTTP/2

[gsnedders]

With the following config:

{
    "check_subdomains": false,
    "server_host": "192.168.22.1",
    "bind_address": false,
    "ports": {
        "http": [],
        "http-private": [],
        "http-public": [],
        "https": [],
        "https-private": [],
        "https-public": [],
        "ws": [5000],
        "wss": [],
        "webtransport-h3": []
    }
}

Still leads to:

[2025-03-11 15:59:59,753 h2 on port 9000] INFO - Starting http2 server on https://192.168.22.1:9000

This is unexpected, as no port has been configured. While this might've been a sensible migration path when adding a new server (I can't recall what the status quo was when we added the H2 server!), it feels extremely surprising now.

Instead of requiring --no-h2 to disable H2, we should just rely on the config.