minor 404 copy update

404.html

@@ -26,8 +26,6 @@
       <h2>404</h2>
       <h1>Page Not Found</h1>
       <p>The specified file was not found on this website. Please check the URL for mistakes and try again.</p>
-      <h3>Why am I seeing this?</h3>
-      <p>This page was generated by the Firebase Command-Line Interface. To modify it, edit the <code>404.html</code> file in your project's configured <code>public</code> directory.</p>
     </div>
   </body>
 </html>