Explicitly pass filter to TarFile.extractall on Python >=3.12

[drammock]

python 3.13 warns loudly about calling TarFile.extractall without specifying the filter param:

[...EARLIER STEPS OF TRACEBACK OMITTED FOR BREVITY...]
    pooch.retrieve(
/opt/mambaforge/envs/mnedev/lib/python3.13/site-packages/pooch/core.py:251: in retrieve
    return processor(str(full_path), action, None)
/opt/mambaforge/envs/mnedev/lib/python3.13/site-packages/pooch/processors.py:121: in __call__
    self._extract_file(fname, self.extract_dir)
/opt/mambaforge/envs/mnedev/lib/python3.13/site-packages/pooch/processors.py:262: in _extract_file
    tar_file.extractall(path=extract_dir)
/opt/mambaforge/envs/mnedev/lib/python3.13/tarfile.py:2321: in extractall
    filter_function = self._get_filter_function(filter)
/opt/mambaforge/envs/mnedev/lib/python3.13/tarfile.py:2286: in _get_filter_function
    warnings.warn(
E   DeprecationWarning: Python 3.14 will, by default, filter extracted tar archives and reject files or modify their metadata. Use the filter argument to control this behavior.

This PR passes explicitly what will become the default in Py3.14. Honestly I'm surprised this warning wasn't causing test failures in your CIs, but on cursory glance I don't spot any obvious culprit (like a filterwarnings in conftest.py or in [pytest.ini_options] of pyproject.toml, or something similar).

Relevant issues/PRs:

[santisoler]

Thanks @drammock for this! Nice catch!

Our tests are catching the warning, but they are not raising an error. See for example: https://github.com/fatiando/pooch/actions/runs/12638921221/job/35216179298#step:13:196

[...]
tests/test_processors.py::test_unpacking[Untar-archive_all-default_path]
tests/test_processors.py::test_unpacking[Untar-archive_all-custom_path]
tests/test_processors.py::test_unpacking_members_then_no_members[Untar-.tar.gz]
tests/test_processors.py::test_unpacking_wrong_members_then_no_members[Untar-.tar.gz]
  /opt/hostedtoolcache/Python/3.13.1/x64/lib/python3.13/site-packages/pooch/processors.py:262: DeprecationWarning: Python 3.14 will, by default, filter extracted tar archives and reject files or modify their metadata. Use the filter argument to control this behavior.
    tar_file.extractall(path=extract_dir)
[...]

I'll open an issue to remind me to add some filterwarnings for our tests.

I'm merging this!