Make search use id index too.

Seems to be faster in general, query planner chooses well.

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -521,7 +521,7 @@ def search(%{assigns: %{user: user}} = conn, %{"q" => query} = params) do
             ^query
           ),
         limit: 20,
-        order_by: [desc: :inserted_at]
+        order_by: [desc: :id]
       )
 
     statuses = Repo.all(q) ++ fetched