REF: Replace os.path with pathlib.Path in pandas_web.py
Replaces `os.path `with `pathlib.Path` in `pandas_web.py`, as suggested by @datapythonista in [61578](https://github.com/pandas-dev/pandas/pull/61578). No functional changes, verified site generation remains correct
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).

I'm resolving the conflicts, it's my previous PR which just got merged