React: Remove redundant default imports of React from code examples

[Victor-M-Giraldo]

Because

Some of the lessons in the React section still had the default React import. This is no longer required.

This PR

• Removed default imports from Class-based components
• Removed default imports from Refs and memoization
• Removed default imports from How to deal with side effects
• Removed default imports from Type checking with proptypes

Issue

Closes #28592

Additional Information

None

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum contributing guide
• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide

[MaoShizhong]

Thanks for removing these. I think you forgot to also remove the redundant imports from Introduction to React Testing, the lesson the original issue was about 😛

[Victor-M-Giraldo]

Oops haha. Got it.

Irrelevant to this issue, but I noticed this in the React Router lesson.

import { createBrowserRouter, RouterProvider } from "react-router-dom";
import React from "react";
import ReactDOM from "react-dom/client";
import routes from "./routes";

const router = createBrowserRouter(routes);

ReactDOM.createRoot(document.getElementById("root")).render(
  <React.StrictMode>
    <RouterProvider router={router} />
  </React.StrictMode>
);

When you make a react app with Vite it doesn't import React, it just does the destructuring directly import { StrictMode } from 'react';. Not sure if that's a huge deal though

[MaoShizhong]

🚀

I'm not particularly fussed about the strict mode import. People are aware about named and default imports already. The React default imports in this PR were actually redundant since they weren't being used at all.