### 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
OS::get_singleton()->print(", ");
						}
						OS::get_singleton()->print("'%s'", AudioDriverManager::get_driver(i)->get_name());
					}
					OS::get_singleton()->print(".\n");
					goto error;
				}
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing audio driver argument, aborting.\n");
				goto error;
			}
		} else if (I->get() == "--text-driver") {
			if (I->next()) {
				text_driver = I->next()->get();
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing text driver argument, aborting.\n");
				goto error;
			}
		} else if (I->get() == "--display-driver") { 
			if (I->next()) {
				display_driver = I->next()->get();
				bool found = false;
				for (int i = 0; i < DisplayServer::get_create_function_count(); i++) {
					if (display_driver == DisplayServer::get_create_function_name(i)) {
						found = true;
					}
				}
				if (!found) {