Unable to install both returns and classes together

# Bug report

## What's wrong

Just doing a simple `poetry add returns` and `poetry add classes` results in:

```
Because no versions of classes match >0.4.0,<0.5.0
and classes (0.4.0) depends on typing_extensions (>=3.10,<4.0), classes (>=0.4.0,<0.5.0) requires typing_extensions (>=3.10,<4.0).
And because returns (0.19.0) depends on typing-extensions (>=4.0,<5.0)
and no versions of returns match >0.19.0,<0.20.0, classes (>=0.4.0,<0.5.0) is incompatible with returns (>=0.19.0,<0.20.0).
So, because ogc depends on both returns (^0.19.0) and classes (^0.4.0), version solving failed.
```

## How is that should be

Should I be able to run both of these libraries together? If so, maybe just a typing-extensions version update is needed?

## System information

- `python` version: 3.9
- `classes` version: 0.4.0
- `returns` version: 0.19.0
- `mypy` version: 0.941