chore: update react imports

Signed-off-by: Paul Schultz <pschultz@pobox.com>

contrib/docs/tutorials/aws-alb-aad-oidc-auth.md

@@ -55,15 +55,15 @@ When using ALB authentication Backstage will only be loaded once the user has su
 - add the following definition just before the app is created (`const app = createApp`):
 
 ```ts
-import React from 'react';
+import { useState, useEffect } from 'react';
 import { UserIdentity } from '@backstage/core-components';
 import { SignInPageProps } from '@backstage/core-app-api';
 import { useApi, configApiRef } from '@backstage/core-plugin-api';
 
 const SampleSignInComponent: any = (props: SignInPageProps) => {
-  const [error, setError] = React.useState<string | undefined>();
+  const [error, setError] = useState<string | undefined>();
   const config = useApi(configApiRef);
-  React.useEffect(() => {
+  useEffect(() => {
     const shouldAuth = !!config.getOptionalConfig('auth.providers.awsalb');
     if (shouldAuth) {
       fetch(`${window.location.origin}/api/auth/awsalb/refresh`)

contrib/docs/tutorials/quickstart-app-plugin/ExampleComponent.md

@@ -3,7 +3,6 @@
 ExampleComponent.tsx reference
 
 ```tsx
-import React from 'react';
 import { Typography, Grid } from '@material-ui/core';
 import { identityApiRef, useApi } from '@backstage/core-plugin-api';
 import {

contrib/docs/tutorials/quickstart-app-plugin/ExampleFetchComponent.md

@@ -3,7 +3,6 @@
 ExampleFetchComponent.tsx reference
 
 ```tsx
-import React from 'react';
 import useAsync from 'react-use/lib/useAsync';
 import Alert from '@material-ui/lab/Alert';
 import { githubAuthApiRef, useApi } from '@backstage/core-plugin-api';

contrib/search/confluence/ConfluenceResultListItem.md

@@ -1,7 +1,6 @@
 ConfluenceResultListItem.tsx reference
 
 ```tsx
-import React from 'react';
 import { Link } from '@backstage/core-components';
 import { IndexableDocument } from '@backstage/plugin-search-common';
 import {