My output refused to change after i changed the code in the ReactDOM.render() method in my index.js file

After running the npx create-react-app my-app, cd my-app, npm start. It launched a browser on localhost:3000. After which I opened the index.js file the ReactDOM.render() method read

ReactDOM.render(
<React.StrictMode>
<App />
</React.StrictMode>
document.getElementById('root')
);
ReactDOM.render(
<h1> Hello, React! </h1>
document.getElementById('root')
);

The output is supposed to show Hello, React!. instead its showing the output from app.js. please I want my output to read “Hello React!”