Update database settings for better performance, see...

Update database settings for better performance, see https://www.drupal.org/project/drupal/issues/2733675

templates/settings.docker.php.twig

@@ -50,7 +50,7 @@ $databases = array(
       'database' => 'drupal',
       'prefix' => '',
       'init_commands' => [
-        'tx_level' => "SET TRANSACTION ISOLATION LEVEL READ COMMITTED;",
+        'isolation_level' => 'SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED',
       ],
     ),
   ),