`req.connection` is deprecated

`req.connection` is [deprecated](https://nodejs.org/api/http.html#http_request_connection) since Node 13.0.0. [`req.socket`](https://nodejs.org/api/http.html#http_request_socket) should be used instead (it's available since Node 0.3.0).

https://github.com/jshttp/forwarded/blob/eb75571c7a3afdbb04a435411c91ad5dbeca7092/index.js#L31