404 template example: remove slash relURL arg

For context, see:

- #9994

/cc @jmooring @dep

content/en/templates/404.md

@@ -35,7 +35,7 @@ This is a basic example of a 404.html template:
 {{ define "main"}}
     <main id="main">
       <div>
-       <h1 id="title"><a href="{{ "/" | relURL }}">Go Home</a></h1>
+       <h1 id="title"><a href="{{ "" | relURL }}">Go Home</a></h1>
       </div>
     </main>
 {{ end }}