[docs]: Updated CodePen links (#4232)

Signed-off-by: Aniruddha Shriwant <aniruddhashriwant@gmail.com>

content/docs/rendering-elements.md

@@ -38,7 +38,7 @@ To render a React element into a root DOM node, pass both to [`ReactDOM.render()
 
 `embed:rendering-elements/render-an-element.js`
 
-[](codepen://rendering-elements/render-an-element)
+**[Try it on CodePen](https://codepen.io/gaearon/pen/ZpvBNJ?editors=1010)**
 
 It displays "Hello, world" on the page.
 
@@ -52,7 +52,7 @@ Consider this ticking clock example:
 
 `embed:rendering-elements/update-rendered-element.js`
 
-[](codepen://rendering-elements/update-rendered-element)
+**[Try it on CodePen](https://codepen.io/gaearon/pen/gwoJZk?editors=1010)**
 
 It calls [`ReactDOM.render()`](/docs/react-dom.html#render) every second from a [`setInterval()`](https://developer.mozilla.org/en-US/docs/Web/API/WindowTimers/setInterval) callback.
 
@@ -66,7 +66,7 @@ It calls [`ReactDOM.render()`](/docs/react-dom.html#render) every second from a
 
 React DOM compares the element and its children to the previous one, and only applies the DOM updates necessary to bring the DOM to the desired state.
 
-You can verify by inspecting the [last example](codepen://rendering-elements/update-rendered-element) with the browser tools:
+You can verify by inspecting the [last example](https://codepen.io/gaearon/pen/gwoJZk?editors=1010) with the browser tools:
 
 ![DOM inspector showing granular updates](../images/docs/granular-dom-updates.gif)