Uprev pint to 0.24.* for python 3.13+ support

[brendan-w]

This was failing with some frozen dataclass errors in python 3.13, making it fail on most modern installs.

...
  File "/home/brendan/.virtualenvs/obd/lib/python3.13/site-packages/pint/delegates/txt_defparser/common.py", line 21, in <module>
    @dataclass(frozen=True)
     ~~~~~~~~~^^^^^^^^^^^^^
  File "/usr/lib64/python3.13/dataclasses.py", line 1295, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash,
                          frozen, match_args, kw_only, slots,
                          weakref_slot)
  File "/usr/lib64/python3.13/dataclasses.py", line 1043, in _process_class
    raise TypeError('cannot inherit frozen dataclass from a '
                    'non-frozen one')
TypeError: cannot inherit frozen dataclass from a non-frozen one

Also corrected some of the package classifiers to indicate that this python library no longer supports python 2. It didn't even with the older 0.20.* Pint, though Pint itself now only supports python 3.9+

Testing

• re-ran all unit tests