remove old test code from marketing_cloud_example

There is some . legacy test code left in submitForm() in marketing_cloud_example, left over from when creating the unit tests.

Please delete the following lines:

    $response = \Drupal::service('marketing_cloud_push.service')
      ->sendMessageToAll('OEl8ODow', [
        "override" => true,
        "messageText" => "New information available!",
        "title" => "Boost your winnings!",
        "subtitle" => "Check your app to see what else is in store.",
        "mutable-content" => true,
        "sendTime" => "2012-10-31 09 =>00",
        "sound" => "MyFile.caf",
        "badge" => "+1",
        "openDirect" => "OD01",
        "customKeys" => [
          "keyA" => "keyA_value",
          "keyB" => "keyB_value"
        ],
        "customPayload" => [ "customA" => "customA_value" ]
      ]);
    var_dump($response);die();