Fixed PHPStan errors introduced in PR #1325. (#2207)

Author: kiatng

app/code/core/Mage/Catalog/Model/Category/Indexer/Product.php

@@ -191,7 +191,7 @@ protected function _registerProductEvent(Mage_Index_Model_Event $event)
     {
         $eventType = $event->getType();
         if ($eventType == Mage_Index_Model_Event::TYPE_SAVE) {
-            /** @var Varien_Object|Mage_Catalog_Model_Product $product */
+            /** @var Mage_Catalog_Model_Product $product */
             $product = $event->getDataObject();
             /**
              * Check if product categories data was changed

app/code/core/Mage/Catalog/Model/Resource/Product/Attribute/Backend/Urlkey.php

@@ -38,7 +38,7 @@ class Mage_Catalog_Model_Resource_Product_Attribute_Backend_Urlkey extends Mage_
     /**
      * Before save
      *
-     * @param Varien_Object $object
+     * @param Mage_Catalog_Model_Product $object
      * @return $this
      */
     public function beforeSave($object)
@@ -58,7 +58,7 @@ public function beforeSave($object)
     /**
      * Refresh product rewrites
      *
-     * @param Varien_Object $object
+     * @param Mage_Catalog_Model_Product $object
      * @return $this
      */
     public function afterSave($object)