08.focus typo (#230)

Author: leo-bjorn

exercises/08.focus/01.problem.flush-sync/README.mdx

@@ -26,7 +26,7 @@ it's easy for them to edit.
 test tab focus with. Good luck!
 
 <callout-info class="aside">
-	This example was uses code from
+	This example uses code from
 	[trellix](https://github.com/remix-run/example-trellix/blob/3379b3d5e9c0173381031e4f062877e8a3696b2e/app/routes/board.%24id/components.tsx).
 </callout-info>