updated readings link

Author: curiouslemur

cal.md

@@ -30,7 +30,7 @@ comment: actual calendar is autogenerated, see `_data/cal.json`
       <ul>
         <li><a href="https://css-tricks.com/how-css-selectors-work/">How CSS Selectors Work</a></li>
         <li><a href="https://developer.mozilla.org/en-US/docs/Learn/CSS/Introduction_to_CSS/Box_model">The Box Model</a></li>
-<li><a href="https://github.com/getify/You-Dont-Know-JS/tree/2nd-ed/scope%20%26%20closures">Chapters 1,2, and 3 from You Don't Know JS: Scope & Closures</a> (this will probably take a minimum of three hours)</li>
+<li><a href="https://github.com/getify/You-Dont-Know-JS/tree/1st-ed/scope%20%26%20closures">Chapters 1,2, and 3 from You Don't Know JS: Scope & Closures</a> (this will probably take a minimum of three hours)</li>
       </ul>
     </div>
   </div>