Remove redundant getCacheTags method from Topmenu

Author: TuVanDev

app/code/Magento/Theme/Block/Html/Topmenu.php

@@ -356,17 +356,6 @@ public function getIdentities()
         return $this->identities;
     }
 
-    /**
-     * Get tags array for saving cache
-     *
-     * @return array
-     * @since 100.1.0
-     */
-    protected function getCacheTags()
-    {
-        return array_merge(parent::getCacheTags(), $this->getIdentities());
-    }
-
     /**
      * Get menu object.
      *