Remove Data providers from the navigation (#126)

modules/layout/app-bar.jsx

@@ -1,6 +1,5 @@
 import React from 'react'
 import { AppBar, Logo, Button } from '@oacore/design'
-import Link from 'next/link'
 
 import styles from './styles.module.css'
 
@@ -12,13 +11,6 @@ const SearchAppBar = ({ children, className, ...restProps }) => (
     {children}
     <AppBar.Item tag="nav" className={styles.navigation}>
       <ul className={styles.navigationList}>
-        <li>
-          <Link href="/data-providers" passHref>
-            <Button tag="a" className={styles.link}>
-              Data providers
-            </Button>
-          </Link>
-        </li>
         <li>
           <Button tag="a" href="//core.ac.uk/services" className={styles.link}>
             Services