[guide] fix a few IIFE examples

Author: ljharb

README.md

@@ -1936,13 +1936,13 @@ Other Style Guides
     (() => {
       const name = 'Skywalker';
       return name;
-    })();
+    }());
 
     // good (guards against the function becoming an argument when two files with IIFEs are concatenated)
     ;(() => {
       const name = 'Skywalker';
       return name;
-    })();
+    }());
     ```
 
     [Read more](http://stackoverflow.com/questions/7365172/semicolon-before-self-invoking-function/7365214%237365214).