fixed typo (#243)

exercises/04.dom/README.mdx

@@ -4,7 +4,7 @@
 
 Often when working with React you'll need to interact with the DOM directly. You
 may need to use a vanilla-js (non-framework-specific) library that needs to
-interact with directly with the DOM. Often to make a UI accessible you need to
+interact directly with the DOM. Often to make a UI accessible you need to
 consider focus management requiring you to call `.focus()` on an input.
 
 Remember that when you do: `<div>hi</div>` that's actually syntactic sugar for a