Update README.mdx (#230)

Author: jsparkdev

exercises/01.managing-ui-state/02.problem.control/README.mdx

@@ -10,6 +10,6 @@ prop on the input.
 
 Once we add the query as the value for the input, we'll also want to have a
 function responsible for updating the query when the user checks or unchecks the
-checkboxes and call that in the `onClick` handler of the checkboxes.
+checkboxes and call that in the `onChange` handler of the checkboxes.
 
 Good luck!