DOC: Run doctests over pandas directory

[mroeschke]

• closes DOC: ongoing fixing of doctests #22459

--ignore-glob="**/test_*.py" is necessary or else unit tests are collected and run

% pytest --doctest-modules pandas --collect-only
...
    <Function test_rolling_consistency_var_debiasing_factors[all_data16-rolling_consistency_cases0-False]>
    <Function test_rolling_consistency_var_debiasing_factors[all_data16-rolling_consistency_cases1-True]>
    <Function test_rolling_consistency_var_debiasing_factors[all_data16-rolling_consistency_cases1-False]>
    <Function test_rolling_consistency_var_debiasing_factors[all_data17-rolling_consistency_cases0-True]>
    <Function test_rolling_consistency_var_debiasing_factors[all_data17-rolling_consistency_cases0-False]>
    <Function test_rolling_consistency_var_debiasing_factors[all_data17-rolling_consistency_cases1-True]>
    <Function test_rolling_consistency_var_debiasing_factors[all_data17-rolling_consistency_cases1-False]>
<Package tseries>
  <DoctestModule frequencies.py>
    <DoctestItem pandas.tseries.frequencies.infer_freq>
  <DoctestModule holiday.py>
    <DoctestItem pandas.tseries.holiday.Holiday.__init__>
<Package util>
  <DoctestModule _decorators.py>
    <DoctestItem pandas.util._decorators.deprecate_kwarg>
  <DoctestModule _validators.py>
    <DoctestItem pandas.util._validators.validate_axis_style_args>

=================================================================== 153109 tests collected in 46.60s ===================================================================