Popups appear in the wrong position with multiple displays

- Move Godot editor to second screen
- Trigger popup e.g. with Ctrl+T
- Popup appears not at the mouse but on the edge of the screen

Probable fix in `go-to-test-command.gd`:
```gdscript
	editor.popup_dialog(popup, Rect2i(
		DisplayServer.mouse_get_position(), #!!
		Vector2.ZERO
	))
```