dataframely breaks in newest polars pre-release due to `PartitioningScheme` being (re)moved from `polars._typing`

With polars https://github.com/pola-rs/polars/releases/tag/py-1.36.0-beta.2 I get an exception when using dataframely.

```
    from dataframely.schema import Schema
.venv/lib/python3.12/site-packages/dataframely/schema.py:17: in <module>
    from polars._typing import FileSource, PartitioningScheme
E   ImportError: cannot import name 'PartitioningScheme' from 'polars._typing'
```