update imports for React 18

Change-Id: Ibc75ce532003a478b31d5d85d84c83a017262041
diff --git a/client/src/App.js b/client/src/App.js
index c05265e..2505137 100644
--- a/client/src/App.js
+++ b/client/src/App.js
@@ -4,7 +4,7 @@
   License: AGPL-3
 */
 import { ThemeProvider } from '@mui/material/styles';
-import React, { useState, useEffect } from 'react'
+import { useState, useEffect } from 'react'
 import { Route, Routes, Navigate } from 'react-router-dom'
 import authManager from './AuthManager'