Update future-functions.md

Author: AlexGuteniev

docs/standard-library/future-functions.md

@@ -1,7 +1,7 @@
 ---
 description: "Learn more about: <future> functions"
 title: "<future> functions"
-ms.date: "11/04/2016"
+ms.date: "08/17/2021"
 f1_keywords: ["future/std::async", "future/std::future_category", "future/std::make_error_code", "future/std::make_error_condition", "future/std::swap"]
 ms.assetid: 1e3acc1e-736a-42dc-ade2-b2fe69aa96bc
 helpviewer_keywords: ["std::async [C++]", "std::future_category [C++]", "std::make_error_code [C++]", "std::make_error_condition [C++]", "std::swap [C++]"]