DOC: fix docstring validation errors for pandas.PeriodIndex

[hlakams]

Addresses #59637.

Fixes:

pandas/ci/code_checks.sh

Lines 84 to 104 in 306385b

	-i "pandas.PeriodIndex.day SA01" \
	-i "pandas.PeriodIndex.day_of_week SA01" \
	-i "pandas.PeriodIndex.day_of_year SA01" \
	-i "pandas.PeriodIndex.dayofweek SA01" \
	-i "pandas.PeriodIndex.dayofyear SA01" \
	-i "pandas.PeriodIndex.days_in_month SA01" \
	-i "pandas.PeriodIndex.daysinmonth SA01" \
	-i "pandas.PeriodIndex.from_fields PR07,SA01" \
	-i "pandas.PeriodIndex.from_ordinals SA01" \
	-i "pandas.PeriodIndex.hour SA01" \
	-i "pandas.PeriodIndex.is_leap_year SA01" \
	-i "pandas.PeriodIndex.minute SA01" \
	-i "pandas.PeriodIndex.month SA01" \
	-i "pandas.PeriodIndex.quarter SA01" \
	-i "pandas.PeriodIndex.qyear GL08" \
	-i "pandas.PeriodIndex.second SA01" \
	-i "pandas.PeriodIndex.to_timestamp RT03,SA01" \
	-i "pandas.PeriodIndex.week SA01" \
	-i "pandas.PeriodIndex.weekday SA01" \
	-i "pandas.PeriodIndex.weekofyear SA01" \
	-i "pandas.PeriodIndex.year SA01" \

[mroeschke]

Thanks @hlakams