MAGETWO-64465: Investigate and fix post-refactoring issues

- removed unused code

Author: rganin

app/code/Magento/Catalog/Model/Product/Option/Type/File.php

@@ -444,23 +444,6 @@ public function parseOptionValue($optionValue, $productOptionValues)
         return null;
     }
 
-    /**
-     * Validate Json serialized value
-     *
-     * @param string $jsonValue - JSON serialized value
-     * @return mixed
-     * @throws SerializationException
-     */
-    private function unserializeJsonValue($jsonValue)
-    {
-        $value = $this->serializer->unserialize($jsonValue);
-        if (json_last_error() === JSON_ERROR_NONE) {
-            return $value;
-        } else {
-            throw new SerializationException(__('Invalid JSON value.'));
-        }
-    }
-
     /**
      * Prepare option value for info buy request
      *