Update article.md

Change "occasional" to "accidental". I think that's what you mean, and the words are not synonymous in English.

1-js/11-async/04-promise-error-handling/article.md

@@ -92,7 +92,7 @@ new Promise((resolve, reject) => {
 }).catch(alert); // ReferenceError: blabla is not defined
 ```
 
-The final `.catch` not only catches explicit rejections, but also occasional errors in the handlers above.
+The final `.catch` not only catches explicit rejections, but also accidental errors in the handlers above.
 
 ## Rethrowing