Investigate some warnings in the tests

[micheles]

• fiona warning

 $ pytest openquake/commands/ -k test_convert_mixed_nrml_from_gpkg
  <frozen _collections_abc>:918: FionaDeprecationWarning: instances of this class -- CRS, geometry, and feature objects -- will become immutable in fiona version 2.0

• chiou_youngs warning

openquake/hazardlib/tests/gsim/chiou_youngs_2014_test.py::BooreEtAl2022Adjustments::test_stress_and_path_adjustments
  /home/michele/oq-engine/openquake/hazardlib/gsim/chiou_youngs_2014.py:500: RuntimeWarning: invalid value encountered in divide
    nl0 = f_nl_scaling * (y_ref / (y_ref + C["phi4"]))

• pytz warning (there is nothing we can do about this, since pandas will depend on pytz at least until version 3.0 :-()

  /home/michele/openquake/lib64/python3.12/site-packages/pytz/tzinfo.py:27: DeprecationWarning: datetime.datetime.utcfromtimestamp() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.fromtimestamp(timestamp, datetime.UTC).
    _epoch = datetime.utcfromtimestamp(0)

• Django warnings (we will have to wait for Django 5.0 for this one)

/home/michele/openquake/lib64/python3.12/site-packages/django/conf/__init__.py:267: RemovedInDjango50Warning: The USE_L10N setting is deprecated. Starting with Django 5.0, localized formatting of data will always be enabled. For example Django will display numbers and dates using the format of the current locale.
    warnings.warn(USE_L10N_DEPRECATED_MSG, RemovedInDjango50Warning)