apply rector rules

src/Bundle/ChillMainBundle/Export/Formatter/SpreadSheetFormatter.php

@@ -126,17 +126,13 @@ class SpreadSheetFormatter implements FormatterInterface
      * The array's keys are the keys in the raw result, and
      * values are the callable which will transform the raw result to
      * displayable result.
-     *
-     * @var array
      */
-    private $cacheDisplayableResult;
+    private ?array $cacheDisplayableResult = null;
 
     /**
      * Whethe `cacheDisplayableResult` is initialized or not.
-     *
-     * @var bool
      */
-    private $cacheDisplayableResultIsInitialized = false;
+    private bool $cacheDisplayableResultIsInitialized = false;
 
     public function __construct(TranslatorInterface $translatorInterface, ExportManager $exportManager)
     {