Merge pull request #2838 from romanstetsyk/part2a-links

update links to react docs for part2a

Author: mluukkai

src/content/2/en/part2a.md

@@ -213,7 +213,7 @@ Even though the application seems to be working, there is a nasty warning in the
 
 ![unique key prop console error](../../images/2/1a.png)
 
-As the linked [React page](https://reactjs.org/docs/lists-and-keys.html#keys) in the error message suggests; the list items, i.e. the elements generated by the _map_ method, must each have a unique key value:  an attribute called <i>key</i>.
+As the linked [React page](https://react.dev/learn/rendering-lists#keeping-list-items-in-order-with-key) in the error message suggests; the list items, i.e. the elements generated by the _map_ method, must each have a unique key value:  an attribute called <i>key</i>.
 
 Let's add the keys:
 
@@ -238,7 +238,7 @@ const App = (props) => {
 
 And the error message disappears.
 
-React uses the key attributes of objects in an array to determine how to update the view generated by a component when the component is re-rendered. More about this is in the [React documentation](https://reactjs.org/docs/reconciliation.html#recursing-on-children).
+React uses the key attributes of objects in an array to determine how to update the view generated by a component when the component is re-rendered. More about this is in the [React documentation](https://react.dev/learn/preserving-and-resetting-state#option-2-resetting-state-with-a-key).
 
 ### Map