[HfFileSystem] Make lpath optional in get_file (fsspec>=2026.9.0) (#4951)
* [HfFileSystem] Make `lpath` optional in `get_file` (fsspec>=2026.9.0)
fsspec 2026.9.0 made `lpath` optional in `AbstractFileSystem.get_file`
(it can be omitted when `outfile` is provided). Our override kept it
required, which the latest `ty` flags as an invalid method override and
fails CI.
Make `lpath=None` in the signature and raise a clear ValueError if
neither `lpath` nor `outfile` is provided. No behavior change otherwise.
* fix get_file branching to match fsspec
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Co-authored-by: Celina Hanouti <hanouticelina@gmail.com>