chore: update react imports

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

packages/app-defaults/src/createApp.test.tsx

@@ -16,7 +16,7 @@
 
 import { screen } from '@testing-library/react';
 import { renderWithEffects } from '@backstage/test-utils';
-import React, { PropsWithChildren } from 'react';
+import { PropsWithChildren } from 'react';
 import { MemoryRouter } from 'react-router-dom';
 import { createApp } from './createApp';
 

packages/app-defaults/src/defaults/components.test.tsx

@@ -15,7 +15,6 @@
  */
 
 import { render, screen } from '@testing-library/react';
-import React from 'react';
 import { MemoryRouter } from 'react-router-dom';
 import { OptionallyWrapInRouter } from './components';
 

packages/app-defaults/src/defaults/components.tsx

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import React, { ReactNode } from 'react';
+import { ReactNode } from 'react';
 import Button from '@material-ui/core/Button';
 import { ErrorPanel, Progress, ErrorPage } from '@backstage/core-components';
 import {

packages/app-defaults/src/defaults/themes.tsx

@@ -14,7 +14,6 @@
  * limitations under the License.
  */
 
-import React from 'react';
 import {
   UnifiedThemeProvider,
   themes as builtinThemes,