remove unused imports, fix lint errors

src/components/header/Header.jsx

@@ -1,28 +1,13 @@
-import React, {
-  useState,
-} from 'react';
+import React from 'react';
 import { Link } from 'react-router-dom';
 import { Link as MuiLink } from '@material-ui/core';
 import AppBar from '@material-ui/core/AppBar';
 import Toolbar from '@material-ui/core/Toolbar';
-import Button from '@material-ui/core/Button';
-import Popover from '@material-ui/core/Popover';
-import Divider from '@material-ui/core/Divider';
-import IconButton from '@material-ui/core/IconButton';
-import AccountCircle from '@material-ui/icons/AccountCircle';
-import AccountCircleOutlinedIcon from '@material-ui/icons/AccountCircleOutlined';
-import { useAuth0 } from '@auth0/auth0-react';
 
 import './header.css';
 import Logo from '../Logo';
 
 export default function Header() {
-  const [anchorEl, setAnchorEl] = useState(null);
-
-  const {
-    logout, isAuthenticated, loginWithPopup,
-  } = useAuth0();
-
   return (
     <AppBar position="relative" className="header">
       <Toolbar id="headerToolbar">
@@ -34,15 +19,6 @@ export default function Header() {
         <Link to="/tutorial">Tutorial</Link>
         {/* This will go to the actual root of the host (robokop.renci.org/#contact), not an internal route in this application */}
         <a href="/#contact">Help</a>
-        <Popover
-          anchorEl={anchorEl}
-          open={Boolean(anchorEl)}
-          onClose={() => setAnchorEl(null)}
-          anchorOrigin={{ vertical: 'bottom', horizontal: 'right' }}
-          transformOrigin={{ vertical: 'top', horizontal: 'right' }}
-        >
-          <Button onClick={() => logout({ returnTo: `${window.location.origin}/logout` })}>Sign Out</Button>
-        </Popover>
       </Toolbar>
     </AppBar>
   );