Update mouse button enum references

tutorials/2d/2d_transforms.rst

@@ -99,7 +99,7 @@ way:
 
     var local_pos = Vector2(10, 20) # local to Control/Node2D
     var ie = InputEventMouseButton.new()
-    ie.button_index = BUTTON_LEFT
+    ie.button_index = MOUSE_BUTTON_LEFT
     ie.position = get_viewport_transform() * (get_global_transform() * local_pos)
     get_tree().input_event(ie)
 

tutorials/ui/custom_gui_controls.rst

@@ -139,7 +139,7 @@ Simply override it in your control. No processing needs to be set.
     extends Control
 
     func _gui_input(event):
-       if event is InputEventMouseButton and event.button_index == BUTTON_LEFT and event.pressed:
+       if event is InputEventMouseButton and event.button_index == MOUSE_BUTTON_LEFT and event.pressed:
            print("Left mouse button was pressed!")
 
  .. code-tab:: csharp