### 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
GLOBAL_DEF_RST_BASIC("rendering/renderer/rendering_method.web", "gl_compatibility"); 
	
	if (rendering_method.is_empty()) {
		rendering_method = GLOBAL_GET("rendering/renderer/rendering_method");
	}
	if (rendering_driver.is_empty()) {
		if (rendering_method == "gl_compatibility") {
			rendering_driver = GLOBAL_GET("rendering/gl_compatibility/driver");
		} else {
			rendering_driver = GLOBAL_GET("rendering/rendering_device/driver");
		}
	}
	
	
	
	OS::get_singleton()->set_current_rendering_driver_name(rendering_driver);
	OS::get_singleton()->set_current_rendering_method(rendering_method);
	
	rendering_driver = rendering_driver.to_lower();
	if (use_custom_res) {
		if (!force_res) {
			window_size.width = GLOBAL_GET("display/window/size/viewport_width");
			window_size.height = GLOBAL_GET("display/window/size/viewport_height");
			if (globals->has_setting("display/window/size/window_width_override") &&
					globals->has_setting("display/window/size/window_height_override")) {
				int desired_width = globals->get("display/window/size/window_width_override");
				if (desired_width > 0) {
					window_size.width = desired_width;
				}
				int desired_height = globals->get("display/window/size/window_height_override");