### 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
PackedStringArray warnings = Node::get_configuration_warnings();
	if (spawn_path.is_empty() || !has_node(spawn_path)) {
		warnings.push_back(RTR("A valid NodePath must be set in the \"Spawn Path\" property in order for MultiplayerSpawner to be able to spawn Nodes."));
	}
	return warnings;
}
void MultiplayerSpawner::add_spawnable_scene(const String &p_path) {
	SpawnableScene sc;
	sc.path = p_path;
	if (Engine::get_singleton()->is_editor_hint()) {
		ERR_FAIL_COND(!FileAccess::exists(p_path));
	}
	spawnable_scenes.push_back(sc);
#ifdef TOOLS_ENABLED
	if (Engine::get_singleton()->is_editor_hint()) {
		return;
	}
#endif
	Node *node = get_spawn_node();
	if (spawnable_scenes.size() == 1 && node && !node->is_connected("child_entered_tree", callable_mp(this, &MultiplayerSpawner::_node_added))) {
		node->connect("child_entered_tree", callable_mp(this, &MultiplayerSpawner::_node_added));
	}
}
int MultiplayerSpawner::get_spawnable_scene_count() const {