tests: write a simple Export test for new indicators + fix depreciation with BrowserKit client

cfr: https://symfony.com/doc/4.4/components/browser_kit.html#creating-a-client

src/Bundle/ChillMainBundle/Test/Export/AbstractExportTest.php

@@ -16,6 +16,7 @@ use Doctrine\ORM\NativeQuery;
 use Doctrine\ORM\QueryBuilder;
 use RuntimeException;
 use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
+use Symfony\Component\BrowserKit\HttpBrowser;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\Security\Core\Role\Role;
 use Traversable;
@@ -332,8 +333,9 @@ abstract class AbstractExportTest extends WebTestCase
      */
     public function testListExportPage()
     {
-        /** @var \Symfony\Component\BrowserKit\Client $client */
-        $client = $this->getClient();
+        /** @var HttpBrowser $client */
+        $client = new HttpBrowser();
+
         $export = $this->getExport();
         $prophet = new \Prophecy\Prophet();
         $container = static::$kernel->getContainer();