MNT: add py313 to test matrix

[tacaswell]

Looks like pint has to be updated

ophyd/tests/test_units.py:7: in <module>
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    import ophyd.units
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ophyd/units.py:4: in <module>
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    import pint
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/site-packages/pint/__init__.py:18: in <module>
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    from .delegates.formatter._format_helpers import formatter
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/site-packages/pint/delegates/__init__.py:12: in <module>
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    from . import txt_defparser
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/site-packages/pint/delegates/txt_defparser/__init__.py:12: in <module>
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    from .defparser import DefParser
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/site-packages/pint/delegates/txt_defparser/defparser.py:10: in <module>
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    from . import block, common, context, defaults, group, plain, system
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/site-packages/pint/delegates/txt_defparser/common.py:23: in <module>
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    @dataclass(frozen=True)
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/dataclasses.py:1295: in wrap
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    return _process_class(cls, init, repr, eq, order, unsafe_hash,
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/opt/hostedtoolcache/Python/3.13.0/x64/lib/python3.13/dataclasses.py:1043: in _process_class
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    raise TypeError('cannot inherit frozen dataclass from a '
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E   TypeError: cannot inherit frozen dataclass from a non-frozen one

[tacaswell]

xref https://github.com/hgrecco/pint/pull/2037