### 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
goto error;
#ifdef TOOLS_ENABLED
		}
#endif
	}
	if (editor || project_manager) {
		Engine::get_singleton()->set_editor_hint(true);
		use_custom_res = false;
		input_map->load_default(); 
	} else {
		input_map->load_from_project_settings(); 
	}
	if (bool(GLOBAL_GET("application/run/disable_stdout"))) {
		quiet_stdout = true;
	}
	if (bool(GLOBAL_GET("application/run/disable_stderr"))) {
		CoreGlobals::print_error_enabled = false;
	};
	if (quiet_stdout) {
		CoreGlobals::print_line_enabled = false;
	}
	Logger::set_flush_stdout_on_print(GLOBAL_GET("application/run/flush_stdout_on_print"));
	OS::get_singleton()->set_cmdline(execpath, main_args, user_args);
	{
		String driver_hints = "";
#ifdef VULKAN_ENABLED
		driver_hints = "vulkan";
#endif
		String default_driver = driver_hints.get_slice(",", 0);