chore(infra): Use Regional Instance Group in the GCP NAT example (#4183)

This example will work once our latest gateway is pushed to GitHub
Container Registry, but to test it for now a few overrides can be added
to the `main.tf` to use our Google Artifact Registry and local module
instead:
```diff
module "gateways" {
--  source = "github.com/firezone/firezone/terraform/modules/google-cloud/apps/gateway-region-instance-group"
++  source = "../../../modules/google-cloud/apps/gateway-region-instance-group"
...
++  container_registry = "us-east1-docker.pkg.dev"
++  image_repo         = "firezone-prod/firezone"
++  image              = "gateway"
}
```

---------

Signed-off-by: Jamil <jamilbk@users.noreply.github.com>
Signed-off-by: Andrew Dryga <andrew@dryga.com>
Co-authored-by: Jamil <jamilbk@users.noreply.github.com>

elixir/apps/web/lib/web/live/sites/show.ex

@@ -283,16 +283,10 @@ defmodule Web.Sites.Show do
   end
 
   def handle_info(
-        %Phoenix.Socket.Broadcast{topic: "presences:group_gateways:" <> _group_id} = event,
+        %Phoenix.Socket.Broadcast{topic: "presences:group_gateways:" <> _group_id},
         socket
       ) do
-    rendered_gateway_ids = Enum.map(socket.assigns.gateways, & &1.id)
-
-    if presence_updates_any_id?(event, rendered_gateway_ids) do
-      {:noreply, reload_live_table!(socket, "gateways")}
-    else
-      {:noreply, socket}
-    end
+    {:noreply, reload_live_table!(socket, "gateways")}
   end
 
   def handle_event(event, params, socket) when event in ["paginate", "order_by", "filter"],