[GD 3.0] Fix stretch mode 2d... again

Objects on the screen were not displayed when the project was played,
because it looked for the values of width and height of menus with old
names (godot 2.1?) For that reason delivered value (0, 0).

main/main.cpp

@@ -1235,7 +1235,7 @@ bool Main::start() {
 
 			String stretch_mode = GLOBAL_DEF("display/stretch/mode", "disabled");
 			String stretch_aspect = GLOBAL_DEF("display/stretch/aspect", "ignore");
-			Size2i stretch_size = Size2(GLOBAL_DEF("display/screen/width", 0), GLOBAL_DEF("display/screen/height", 0));
+			Size2i stretch_size = Size2(GLOBAL_DEF("display/window/width", 0), GLOBAL_DEF("display/window/height", 0));
 
 			SceneTree::StretchMode sml_sm = SceneTree::STRETCH_MODE_DISABLED;
 			if (stretch_mode == "2d")