Support newer semchunk

Semchunk is now on version 3.2.1, as far as I can tell, to support it we'd merely need to change

https://github.com/docling-project/docling-core/blob/main/docling_core/transforms/chunker/hybrid_chunker.py#L227

```diff
- segments = sem_chunker.chunk(text)
+ segments = sem_chunker(text)
```

and reflect the version bump in pyproject.toml

I've experimentally done this for myself and it appears to work.

Happy to PR if this upgrade is desirable.