### 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
return p_str.replace("%20", " ");
}
static String get_full_version_string() {
	String hash = String(VERSION_HASH);
	if (!hash.is_empty()) {
		hash = "." + hash.left(9);
	}
	return String(VERSION_FULL_BUILD) + hash;
}
void initialize_physics() {
	
	physics_server_3d = PhysicsServer3DManager::get_singleton()->new_server(
			GLOBAL_GET(PhysicsServer3DManager::setting_property_name));
	if (!physics_server_3d) {
		
		physics_server_3d = PhysicsServer3DManager::get_singleton()->new_default_server();
	}
	ERR_FAIL_COND(!physics_server_3d);
	physics_server_3d->init();
	
	physics_server_2d = PhysicsServer2DManager::get_singleton()->new_server(
			GLOBAL_GET(PhysicsServer2DManager::get_singleton()->setting_property_name));
	if (!physics_server_2d) {
		
		physics_server_2d = PhysicsServer2DManager::get_singleton()->new_default_server();
	}
	ERR_FAIL_COND(!physics_server_2d);
	physics_server_2d->init();
}
void finalize_physics() {