Fix scribble bird path

public-apps/sd_controlnet.livemd

@@ -80,11 +80,10 @@ serving =
 ## Scribble bird
 
 ```elixir
-Kino.Text.new("Scribble Bird")
-livebook_dir = Path.absname(__DIR__)
+Kino.Text.new("Scribble Bird") |> Kino.render()
 
 bird_file_input =
-  Kino.Input.text("Bird file path", default: livebook_dir <> "/scribble_bird.png")
+  Kino.Input.text("Bird file path", default: "/public-apps/scribble_bird.png")
 ```
 
 ```elixir
@@ -111,7 +110,7 @@ Kino.Layout.grid([
 ```
 
 ```elixir
-Kino.Text.new("Generate image ...")
+Kino.Text.new("Generate image ...") |> Kino.render()
 
 output =
   Nx.Serving.run(serving, %{