### 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.
return p_type == "GDScript";
}
String GDScriptLanguage::get_global_class_name(const String &p_path, String *r_base_type, String *r_icon_path) const {
	Error err;
	Ref<FileAccess> f = FileAccess::open(p_path, FileAccess::READ, &err);
	if (err) {
		return String();
	}
	String source = f->get_as_utf8_string();
	GDScriptParser parser;
	err = parser.parse(source, p_path, false);
	const GDScriptParser::ClassNode *c = parser.get_tree();
	if (!c) {
		return String(); 
	}
	/* **WARNING**
	 *
	 * This function is written with the goal to be *extremely* error tolerant, as such
	 * it should meet the following requirements:
	 *
	 * - It must not rely on the analyzer (in fact, the analyzer must not be used here),
	 *   because at the time global classes are parsed, the dependencies may not be present
	 *   yet, hence the function will fail (which is unintended).
	 * - It must not fail even if the parsing fails, because even if the file is broken,