Remove Anon Login, as FTP code never checks for anon login

[luke-goddard]

Hi great project!

I was worried that the scanner tried to log into FTP servers when I saw this.

AnonymousLogin bool   `json:"anonymousLogin"`

After reviewing the FTP module the check is never performed and the field is never filled, so I think it makes sense to delete it from the results struct.

func (p *FTPPlugin) Run(conn net.Conn, timeout time.Duration, target plugins.Target) (*plugins.Service, error) {
	response, err := utils.Recv(conn, timeout)
	if err != nil {
		return nil, err
	}
	if len(response) == 0 {
		return nil, nil
	}

	matches := ftpResponse.FindStringSubmatch(string(response))
	if matches == nil {
		return nil, nil
	}

	payload := plugins.ServiceFTP{
		Banner: string(response),
	}

	return plugins.CreateServiceFrom(target, payload, false, "", plugins.TCP), nil
}

[UNC1739]

Thanks @luke-goddard!