### 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
physics_server_3d->finish();
	memdelete(physics_server_3d);
	physics_server_2d->finish();
	memdelete(physics_server_2d);
}
void finalize_display() {
	rendering_server->finish();
	memdelete(rendering_server);
	memdelete(display_server);
}
void initialize_navigation_server() {
	ERR_FAIL_COND(navigation_server_3d != nullptr);
	navigation_server_3d = NavigationServer3DManager::new_default_server();
	navigation_server_2d = memnew(NavigationServer2D);
}
void finalize_navigation_server() {
	memdelete(navigation_server_3d);
	navigation_server_3d = nullptr;
	memdelete(navigation_server_2d);
	navigation_server_2d = nullptr;
}
void initialize_theme_db() {
	theme_db = memnew(ThemeDB);
	theme_db->initialize_theme();
}
void finalize_theme_db() {