Update article.md

fix typo intentially -> intentionally

1-js/09-classes/02-class-inheritance/article.md

@@ -499,7 +499,7 @@ In the example below a non-method syntax is used for comparison. `[[HomeObject]]
 
 ```js run
 let animal = {
-  eat: function() { // intentially writing like this instead of eat() {...
+  eat: function() { // intentionally writing like this instead of eat() {...
     // ...
   }
 };