wrong formid used in Constructor

Problem/Motivation

While working on this issue #3359357 I observed the wrong formid was used in constructor

 protected function getEditableConfigNames() {
    return [
      'nginx_proxy_manager_connector.settings',
    ];
  }

and formid used in service
$this->config = $configFactory->get('nginx_proxy_manager_connector.nginxproxysettings');

Steps to reproduce

Proposed resolution

$this->config = $configFactory->get('nginx_proxy_manager_connector.settings');