show variance when hovering over generics

```py
class Foo[T]:
    def foo(self) -> T: ...
```

both ty and pyright do this:

<img width="314" height="102" alt="Image" src="https://github.com/user-attachments/assets/15eea4d7-ddb5-4a4f-95b9-8efc9b28d80e" />

pyrefly only shows this:

<img width="341" height="78" alt="Image" src="https://github.com/user-attachments/assets/8e6b9788-a295-4a77-a450-a3ad12c9f033" />