Remove minor typo in React getting started (aws-amplify#4783)

Removed a superfluous letter u from the React getting started setup guide.

Author: sdstolworthy

src/fragments/start/getting-started/react/setup.mdx

@@ -84,6 +84,6 @@ import awsExports from './aws-exports';
 Amplify.configure(awsExports);
 ```
 
-And that's all it takes to configure Amplify. As you add or remove categories and make updates to your backend configuration using the Amplify CLI, the configuration in **aws-exports.js** will update automatically.u
+And that's all it takes to configure Amplify. As you add or remove categories and make updates to your backend configuration using the Amplify CLI, the configuration in **aws-exports.js** will update automatically.
 
 Now that your React app is set up and Amplify is initialized, you can add an API in the next step.