Replace put_opts with put_options in subscriptions guide (#1111)

`put_opts` is deprecated since `absinthe_phoenix` v1.4.1.

guides/subscriptions.md

@@ -116,7 +116,7 @@ defmodule MyAppWeb.UserSocket do
 
   def connect(params, socket) do
     current_user = current_user(params)
-    socket = Absinthe.Phoenix.Socket.put_opts(socket, context: %{
+    socket = Absinthe.Phoenix.Socket.put_options(socket, context: %{
       current_user: current_user
     })
     {:ok, socket}