GitHub pages in Gds-attic is not maintained

Perhaps it should be retired to the attic! Heh. In the meantime, I am changing
this link to just be a link to the organisation, which is fine.

index.html

@@ -23,7 +23,7 @@ <h1>Government Digital Service</h1>
 
     <p>
       As well as this account, we use the
-      <a href="https://gds-attic.github.io/">GDS attic GitHub account</a> to store
+      <a href="https://github.com/gds-attic">GDS attic GitHub account</a> to store
       repositories that we've used but no longer maintain.
     </p>