DOC: ex03 - no fix required
- xref #56804

Used this script to validate:

```py
import subprocess as sp

def validate_func(func_name):
    proc = sp.Popen(['./scripts/validate_docstrings.py', '--errors=EX03', func_name], stdout=sp.PIPE, stderr=sp.PIPE)
    proc.wait()
    out = proc.stderr.read().decode().strip()
    return out.endswith(f'Docstring for "{func_name}" correct. :)')

funcs = ['pandas.DataFrame.var',
 'pandas.DatetimeIndex.day_name',
 'pandas.core.groupby.DataFrameGroupBy.apply',
 'pandas.DatetimeIndex.month_name',
 'pandas.core.groupby.DataFrameGroupBy.hist',
 'pandas.core.groupby.SeriesGroupBy.apply',
 'pandas.core.groupby.SeriesGroupBy.transform',
 'pandas.DataFrame.hist',
 'pandas.DataFrame.tz_localize',
 'pandas.CategoricalIndex.set_categories',
 'pandas.core.groupby.DataFrameGroupBy.boxplot',
 'pandas.core.groupby.SeriesGroupBy.pipe',
 'pandas.DataFrame.plot.bar',
 'pandas.DataFrame.tz_convert',
 'pandas.core.groupby.DataFrameGroupBy.pipe',
 'pandas.DataFrame.skew',
 'pandas.core.window.rolling.Rolling.corr']

for func in funcs:
    print(func, validate_func(func))
```

Let me know if it's too many at once.
Thanks @asishm 