### Godot version

4.0-rc1

### System information

Windows 10

### Issue description

The code: `@export @onready var camera_system : Node3D`

Is throwing: `Line 5:The "@onready" annotation will make the default value to be set after the "@export" takes effect and will override it. (Warning treated as error.)` and is crashing the game.

Unchecking "Treat Warning as Errors" seems to have no effect:

![imagen](https://user-images.githubusercontent.com/248383/217900756-8e214c40-68fb-4fb2-8509-a1e689725930.png)

![imagen](https://user-images.githubusercontent.com/248383/217901253-3b758ebc-48e9-40fe-8d77-16fce7cbae88.png)


### Steps to reproduce

- Write `@export @onready var some_var : Node3D`
- In Project Settings, uncheck `Treat Warning as Errors`
- Try to run the project, a `Parser Error` will be thrown.

### Minimal reproduction project

It's as simple as adding one line of code, so I'm not sure a MRP is needed.
#ifdef TOOLS_ENABLED
	HashMap<StringName, Variant>::ConstIterator E = member_default_values_cache.find(p_property);
	if (E) {
		r_value = E->value;
		return true;
	}
	if (base_cache.is_valid()) {
		return base_cache->get_property_default_value(p_property, r_value);
	}
#endif
	return false;
}
ScriptInstance *GDScript::instance_create(Object *p_this) {
	GDScript *top = this;
	while (top->_base) {
		top = top->_base;
	}
	if (top->native.is_valid()) {
		if (!ClassDB::is_parent_class(p_this->get_class_name(), top->native->get_name())) {
			if (EngineDebugger::is_active()) {
				GDScriptLanguage::get_singleton()->debug_break_parse(_get_debug_path(), 1, "Script inherits from native type '" + String(top->native->get_name()) + "', so it can't be assigned to an object of type: '" + p_this->get_class() + "'");
			}
			ERR_FAIL_V_MSG(nullptr, "Script inherits from native type '" + String(top->native->get_name()) + "', so it can't be assigned to an object of type '" + p_this->get_class() + "'" + ".");
		}
	}
	Callable::CallError unchecked_error;
	return _create_instance(nullptr, 0, p_this, Object::cast_to<RefCounted>(p_this) != nullptr, unchecked_error);
}
PlaceHolderScriptInstance *GDScript::placeholder_instance_create(Object *p_this) {