### Godot version

4.1.beta.a83eb16fb

### System information

Arch Linux

### Issue description

When attempting to have a scene load a resource that uses a script that exports a var of Callable type, a parse error will occur due to Callable not being serializable.

### Steps to reproduce

Create new project.
create a resource script that exports a Callable type:

```
class_name BreakStuff
extends Resource
@export var something: Callable
```

create a .tres file that uses the script.

create a scene that uses that resource, such as with a script like

```
extends Node
@export var stuff: Resource
```

set that resource to that .tres file.

close project and reopen.

Be greeted with error message about a parse error and be unable to open that scene.

Within plain text of .tscn file you can see a line that reads
something =

which causes a parse error as something has nothing to be set to.



### Minimal reproduction project

N/A
return spawnable_scenes.size();
}
String MultiplayerSpawner::get_spawnable_scene(int p_idx) const {
	ERR_FAIL_INDEX_V(p_idx, (int)spawnable_scenes.size(), "");
	return spawnable_scenes[p_idx].path;
}
void MultiplayerSpawner::clear_spawnable_scenes() {
	spawnable_scenes.clear();
#ifdef TOOLS_ENABLED
	if (Engine::get_singleton()->is_editor_hint()) {
		return;
	}
#endif
	Node *node = get_spawn_node();
	if (node && node->is_connected("child_entered_tree", callable_mp(this, &MultiplayerSpawner::_node_added))) {
		node->disconnect("child_entered_tree", callable_mp(this, &MultiplayerSpawner::_node_added));
	}
}
Vector<String> MultiplayerSpawner::_get_spawnable_scenes() const {
	Vector<String> ss;
	ss.resize(spawnable_scenes.size());
	for (int i = 0; i < ss.size(); i++) {
		ss.write[i] = spawnable_scenes[i].path;
	}
	return ss;
}
void MultiplayerSpawner::_set_spawnable_scenes(const Vector<String> &p_scenes) {