### Godot version

master

### System information

Ubuntu

### Issue description

I think one of the recent changes wrapped the project converter in `#ifndef DISABLE_DEPRECATED` but missed the coresponding code in `main.cpp` (and potentially other places).
```
main/main.cpp: In static member function 'static bool Main::start()':
main/main.cpp:2551:33: error: 'ProjectConverter3To4' was not declared in this scope
 2551 |                 int exit_code = ProjectConverter3To4(converter_max_kb_file, converter_max_line_length).convert();
      |                                 ^~~~~~~~~~~~~~~~~~~~
main/main.cpp:2556:33: error: 'ProjectConverter3To4' was not declared in this scope
 2556 |                 int exit_code = ProjectConverter3To4(converter_max_kb_file, converter_max_line_length).validate_conversion();
```

### Steps to reproduce

for instance, try to compile with `deprecated = "no"` in your `custom.py`.

### Minimal reproduction project

n/a
cs_aspect = Window::CONTENT_SCALE_ASPECT_KEEP_WIDTH;
			} else if (stretch_aspect == "keep_height") {
				cs_aspect = Window::CONTENT_SCALE_ASPECT_KEEP_HEIGHT;
			} else if (stretch_aspect == "expand") {
				cs_aspect = Window::CONTENT_SCALE_ASPECT_EXPAND;
			}
			sml->get_root()->set_content_scale_mode(cs_sm);
			sml->get_root()->set_content_scale_aspect(cs_aspect);
			sml->get_root()->set_content_scale_size(stretch_size);
			sml->get_root()->set_content_scale_factor(stretch_scale);
			sml->set_auto_accept_quit(GLOBAL_GET("application/config/auto_accept_quit"));
			sml->set_quit_on_go_back(GLOBAL_GET("application/config/quit_on_go_back"));
			String appname = GLOBAL_GET("application/config/name");
			appname = TranslationServer::get_singleton()->translate(appname);
#ifdef DEBUG_ENABLED
			/
			/
			/
			DisplayServer::get_singleton()->window_set_title(vformat("%s (DEBUG)", appname));
#else
			DisplayServer::get_singleton()->window_set_title(appname);
#endif
			bool snap_controls = GLOBAL_GET("gui/common/snap_controls_to_pixels");
			sml->get_root()->set_snap_controls_to_pixels(snap_controls);
			bool font_oversampling = GLOBAL_GET("gui/fonts/dynamic_fonts/use_oversampling");
			sml->get_root()->set_use_font_oversampling(font_oversampling);
			int texture_filter = GLOBAL_GET("rendering/textures/canvas_textures/default_texture_filter");
			int texture_repeat = GLOBAL_GET("rendering/textures/canvas_textures/default_texture_repeat");
			sml->get_root()->set_default_canvas_item_texture_filter(
					Viewport::DefaultCanvasItemTextureFilter(texture_filter));