Fix import of Worksheet from xlsxwriter

Checks

[X] I have checked that this issue has not already been reported.
[X] I have confirmed this bug exists on the latest version of Polars.

Reproducible example

# polars/dataframe/frame.py

from xlsxwriter import Workbook, Worksheet # Worksheet isn't exposed in xlsxwriter's __init__.py

from xlsxwriter.worksheet import Worksheet # Worksheet just needs to be imported from the worksheet module instead

Log output

N/A

Issue description

I noticed that pyright was complaining about all occurrences of df.write_excel() because the type of "Worksheet" was unknown. Looks like the Worksheet import in the frame.py module just needs to be imported from xlxswriter's worksheet module instead of the top level xlsxwriter namespace. Also, I'm happy to contribute this fix if needed!

Expected behavior

No pyright errors because it is able to resolve the import.

Installed versions

``` --------Version info--------- Polars: 1.6.0 Index type: UInt32 Platform: Windows-11-10.0.22631-SP0 Python: 3.12.5 (tags/v3.12.5:ff3bc82, Aug 6 2024, 20:45:27) [MSC v.1940 64 bit (AMD64)] ----Optional dependencies---- adbc_driver_manager altair cloudpickle connectorx 0.3.3 deltalake fastexcel fsspec gevent great_tables matplotlib nest_asyncio numpy 2.1.0 openpyxl pandas pyarrow pydantic pyiceberg sqlalchemy torch xlsx2csv xlsxwriter 3.2.0 ```

pola-rs / polars