### 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.
IdentifierNode *id = static_cast<IdentifierNode *>(p_previous_operand);
			switch (id->source) {
				case IdentifierNode::LOCAL_VARIABLE:
					source_variable = id->variable_source;
					id->variable_source->usages--;
					break;
				case IdentifierNode::LOCAL_CONSTANT:
					id->constant_source->usages--;
					break;
				case IdentifierNode::FUNCTION_PARAMETER:
					id->parameter_source->usages--;
					break;
				case IdentifierNode::LOCAL_ITERATOR:
				case IdentifierNode::LOCAL_BIND:
					id->bind_source->usages--;
					break;
				default:
					break;
			}
#endif
		} break;
		case Node::SUBSCRIPT:
			
			break;
		default:
			push_error(R"(Only identifier, attribute access, and subscription access can be used as assignment target.)");
			return parse_expression(false); 
	}
	AssignmentNode *assignment = alloc_node<AssignmentNode>();
	reset_extents(assignment, p_previous_operand);