Fix missing signal connection in code sample in Making HTTP requests (#6620)

tutorials/networking/http_request_class.rst

@@ -38,6 +38,7 @@ Below is all the code we need to make it work. The URL points to an online API m
 
         func _ready():
             $HTTPRequest.connect("request_completed", self, "_on_request_completed")
+            $Button.connect("pressed", self, "_on_Button_pressed")
 
         func _on_Button_pressed():
             $HTTPRequest.request("http://www.mocky.io/v2/5185415ba171ea3a00704eed")