Remove unused onAddTask prop and useContext imports from task example

AddTask no longer needs an onAddTask prop or useContext now that the
component reads dispatch directly from context via useTasksDispatch.

Author: danrday

src/content/learn/managing-state.md

@@ -887,10 +887,10 @@ const initialTasks = [
 ```
 
 ```js src/AddTask.js
-import { useState, useContext } from 'react';
+import { useState } from 'react';
 import { useTasksDispatch } from './TasksContext.js';
 
-export default function AddTask({ onAddTask }) {
+export default function AddTask() {
   const [text, setText] = useState('');
   const dispatch = useTasksDispatch();
   return (
@@ -916,7 +916,7 @@ let nextId = 3;
 ```
 
 ```js src/TaskList.js
-import { useState, useContext } from 'react';
+import { useState } from 'react';
 import { useTasks, useTasksDispatch } from './TasksContext.js';
 
 export default function TaskList() {