### Godot version

v4.1.1.stable.official [bd6af8e0e]

### System information

Windows 10

### Issue description

As said in the Title Custom Class Documentation a Function cannot return 'Variant' and will instead be shown to return void, even though Built-in Classes are shown to return 'Variant', an example would be 'Array'
![image](https://github.com/godotengine/godot/assets/34311843/fb8ad532-c37a-43c0-a95f-d70af7ea6894)
![image](https://github.com/godotengine/godot/assets/34311843/3cc1e07b-02e1-4f33-bc98-0fa016b4d864)

### Steps to reproduce

```gdscript
extends Node
class_name CustomClass

func VariantFunction() -> Variant:
	return 10
``` 
Now when checking the Generated Documentation it will appear like: `void VariantFunction()`

### Minimal reproduction project

N/A
break;
				}
				if (m_var->property == GDP::VariableNode::PROP_SETGET) {
					if (m_var->setter_pointer != nullptr) {
						prop_doc.setter = m_var->setter_pointer->name;
					}
					if (m_var->getter_pointer != nullptr) {
						prop_doc.getter = m_var->getter_pointer->name;
					}
				}
				if (m_var->initializer && m_var->initializer->is_constant) {
					prop_doc.default_value = m_var->initializer->reduced_value.get_construct_string().replace("\n", "");
				}
				prop_doc.overridden = false;
				doc.properties.push_back(prop_doc);
			} break;
			case GDP::ClassNode::Member::ENUM: {
				const GDP::EnumNode *m_enum = member.m_enum;
				StringName name = m_enum->identifier->name;
				p_script->member_lines[name] = m_enum->start_line;
				DocData::EnumDoc enum_doc;
				enum_doc.description = m_enum->doc_data.description;
				enum_doc.is_deprecated = m_enum->doc_data.is_deprecated;
				enum_doc.is_experimental = m_enum->doc_data.is_experimental;
				doc.enums[name] = enum_doc;
				for (const GDP::EnumNode::Value &val : m_enum->values) {
					DocData::ConstantDoc const_doc;
					const_doc.name = val.identifier->name;