Added missing semicolon

To be consistent, I added a semicolon after a `let` command

Author: Mathias Bockwoldt

1-js/04-object-basics/01-object/article.md

@@ -205,7 +205,7 @@ let obj = {
   for: 1,
   let: 2,
   return: 3
-}
+};
 
 alert( obj.for + obj.let + obj.return );  // 6
 ```