### 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.
if (has_method(CoreStringNames::get_singleton()->_to_string)) {
		Callable::CallError ce;
		Variant ret = callp(CoreStringNames::get_singleton()->_to_string, nullptr, 0, ce);
		if (ce.error == Callable::CallError::CALL_OK) {
			if (ret.get_type() != Variant::STRING) {
				if (r_valid) {
					*r_valid = false;
				}
				ERR_FAIL_V_MSG(String(), "Wrong type for " + CoreStringNames::get_singleton()->_to_string + ", must be a String.");
			}
			if (r_valid) {
				*r_valid = true;
			}
			return ret.operator String();
		}
	}
	if (r_valid) {
		*r_valid = false;
	}
	return String();
}
Ref<Script> GDScriptInstance::get_script() const {