s/Mozilla Developer Network/MDN Web Docs (#728)

"Mozilla Developer Network" was recently renamed to "MDN Web Docs". This name change is mentioned in the description of https://github.com/mdn/: "Data and tools related to MDN Web Docs (formerly Mozilla Developer Network, formerly Mozilla Developer Center...)".

content/docs/accessibility.md

@@ -140,7 +140,7 @@ Read more about the use of these elements to enhance accessibility here:
 Our React applications continuously modify the HTML DOM during runtime, sometimes leading to keyboard focus being lost or set to an unexpected element. In order to repair this, 
 we need to programmatically nudge the keyboard focus in the right direction. For example, by resetting keyboard focus to a button that opened a modal window after that modal window is closed.
 
-The Mozilla Developer Network takes a look at this and describes how we can build [keyboard-navigable JavaScript widgets](https://developer.mozilla.org/en-US/docs/Web/Accessibility/Keyboard-navigable_JavaScript_widgets).
+MDN Web Docs takes a look at this and describes how we can build [keyboard-navigable JavaScript widgets](https://developer.mozilla.org/en-US/docs/Web/Accessibility/Keyboard-navigable_JavaScript_widgets).
 
 To set focus in React, we can use [Refs to DOM elements](refs-and-the-dom.html).