doc: clarify IncomingMessage.destroy() description

State that the 'error' event is emitted on the underlying socket, not
the IncomingMessage object.

PR-URL: https://github.com/nodejs/node/pull/30255


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>