fix: large message crashes SubscribersNotification

`handle_call/3` has a default timeout of 5s. Large messages (e.g.
inserting 1 million rows) may take longer that this, which causes the
GenServer to crash. Set it to `:infinity` instead.

Author: soedirgo

server/lib/realtime/subscribers_notification.ex

@@ -10,7 +10,7 @@ defmodule Realtime.SubscribersNotification do
   Send notification events via Phoenix Channels to subscribers
   """
   def notify(txn) do
-    GenServer.call(__MODULE__, {:notify, txn})
+    GenServer.call(__MODULE__, {:notify, txn}, :infinity)
   end
 
   @impl true