Fix numpy deprecation warnings

[martinholmer]

@hdoupe, when you fix issue #132 so that ParamTools works with Python 3.12, please also fix the marshmallow deprecation warnings listed below. These are warnings generated by GitHub testing of Tax-Calculator in early May 2024. These warnings seem to arise because of the way ParamTools is using the marshmallow package. Perhaps this use was OK when ParamTools 0.18.0 was developed over three years ago using an older version of marshmallow, but with the newer versions of marshmallow the usage raises a deprecation warning. My understanding of a deprecation warning is that ParamsTool's current usage of marshmallow will eventually generate a fatal error, and so Tax-Calculator will stop working.

=============================== warnings summary ===============================

../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:948
../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:948
../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:948
  /usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:948: RemovedInMarshmallow4Warning: The 'missing' argument to fields is deprecated. Use 'load_default' instead.
    super().__init__(**kwargs)

../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:571
../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:571
  /usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:571: RemovedInMarshmallow4Warning: The 'missing' argument to fields is deprecated. Use 'load_default' instead.
    super().__init__(default=default, dump_default=dump_default, **kwargs)

../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:1562
../../../../../usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:1562
  /usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:1562: RemovedInMarshmallow4Warning: The 'missing' argument to fields is deprecated. Use 'load_default' instead.
    super().__init__(**kwargs)

taxcalc/tests/test_parameters.py::test_params_class[revision1-error]
taxcalc/tests/test_parameters.py::test_params_class[revision12-raise]
  /usr/share/miniconda/envs/taxcalc-dev/lib/python3.9/site-packages/marshmallow/fields.py:952: DeprecationWarning: Conversion of an array with ndim > 0 to a scalar is deprecated, and will error in future. Ensure you extract a single element from your array before performing this operation. (Deprecated NumPy 1.25.)
    return self.num_type(value)

========= 279 passed, 129 deselected, 9 warnings in 1238.58s (0:20:38) =========

[martinholmer]

Using ParamTools 0.18.2 makes most of the deprecation warnings originally reported in issue #133 go away. However, there are still two remaining warnings:

@hdoupe, is this numpy deprecation warning caused by marshmallow misusing numpy or is it cased by the test code in Tax-Calculator? Depending on your answer, what changes would you recommend to eliminate the remaining deprecation warnings?

CC @jdebacker