### Godot version

v4.0.beta14.official [28a24639c]

### System information

MacOS 12.6.2

### Issue description

Beta 14 throws an error for custom `@icon`, e.g.
```
class_name StateMachine extends Node

@icon("res://assets/icons/state_machine.svg")
```
> Annotation "`@icon`" is not allowed in this level.

In beta 13 and before that worked fine.

### Steps to reproduce

1. Add a custom `@icon` in a custom node script.
2. Error message: Annotation "`@icon`" is not allowed in this level.

There are possibly other errors because a `class_name` node is now not recognized if extended by other classes, but they should resolve if `@icon` is removed.

### Minimal reproduction project

N/A
SubscriptNode *attribute = alloc_node<SubscriptNode>();
	reset_extents(attribute, p_previous_operand);
	update_extents(attribute);
	if (for_completion) {
		bool is_builtin = false;
		if (p_previous_operand && p_previous_operand->type == Node::IDENTIFIER) {
			const IdentifierNode *id = static_cast<const IdentifierNode *>(p_previous_operand);
			Variant::Type builtin_type = get_builtin_type(id->name);
			if (builtin_type < Variant::VARIANT_MAX) {
				make_completion_context(COMPLETION_BUILT_IN_TYPE_CONSTANT_OR_STATIC_METHOD, builtin_type, true);
				is_builtin = true;
			}
		}
		if (!is_builtin) {
			make_completion_context(COMPLETION_ATTRIBUTE, attribute, -1, true);
		}
	}
	attribute->base = p_previous_operand;
	if (!consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected identifier after "." for attribute access.)")) {
		complete_extents(attribute);
		return attribute;
	}
	attribute->is_attribute = true;
	attribute->attribute = parse_identifier();
	complete_extents(attribute);
	return attribute;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_subscript(ExpressionNode *p_previous_operand, bool p_can_assign) {