### 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
}
					ERR_CONTINUE_MSG(!n, vformat("Path in autoload not a node or script: %s.", info.path));
					n->set_name(info.name);
					/
					to_add.push_back(n);
					if (info.is_singleton) {
						for (int i = 0; i < ScriptServer::get_language_count(); i++) {
							ScriptServer::get_language(i)->add_global_constant(info.name, n);
						}
					}
				}
				for (Node *E : to_add) {
					sml->get_root()->add_child(E);
				}
				Engine::get_singleton()->startup_benchmark_end_measure(); /
			}
		}
#ifdef TOOLS_ENABLED
		EditorNode *editor_node = nullptr;
		if (editor) {
			Engine::get_singleton()->startup_benchmark_begin_measure("editor");
			editor_node = memnew(EditorNode);
			sml->get_root()->add_child(editor_node);
			if (!_export_preset.is_empty()) {
				editor_node->export_preset(_export_preset, positional_arg, export_debug, export_pack_only);
				game_path = ""; /
			}
			Engine::get_singleton()->startup_benchmark_end_measure();
			editor_node->set_use_startup_benchmark(use_startup_benchmark, startup_benchmark_file);
			/