added minor clarification. (#1672)

* added minor clarification.

* Update CppCoreGuidelines.md

Updated comment.

* Update CppCoreGuidelines.md

CppCoreGuidelines.md

@@ -1493,7 +1493,7 @@ In the following example, it is not clear from the interface what `time_to_blink
 
 ##### Example, good
 
-`std::chrono::duration` types (C++11) helps making the unit of time duration explicit.
+`std::chrono::duration` types helps making the unit of time duration explicit.
 
     void blink_led(milliseconds time_to_blink) // good -- the unit is explicit
     {