DOC: fix SA01,ES01 for pandas.Period.freqstr (#59661)

Author: tuhinsharma121

ci/code_checks.sh

@@ -73,7 +73,6 @@ if [[ -z "$CHECK" || "$CHECK" == "docstrings" ]]; then
         -i "pandas.NA SA01" \
         -i "pandas.NaT SA01" \
         -i "pandas.Period.freq GL08" \
-        -i "pandas.Period.freqstr SA01" \
         -i "pandas.Period.ordinal GL08" \
         -i "pandas.Period.strftime PR01,SA01" \
         -i "pandas.Period.to_timestamp SA01" \

pandas/_libs/tslibs/period.pyx

@@ -2607,6 +2607,17 @@ cdef class _Period(PeriodMixin):
         """
         Return a string representation of the frequency.
 
+        This property provides the frequency string associated with the `Period`
+        object. The frequency string describes the granularity of the time span
+        represented by the `Period`. Common frequency strings include 'D' for
+        daily, 'M' for monthly, 'Y' for yearly, etc.
+
+        See Also
+        --------
+        Period.asfreq : Convert Period to desired frequency, at the start or end
+            of the interval.
+        period_range : Return a fixed frequency PeriodIndex.
+
         Examples
         --------
         >>> pd.Period('2020-01', 'D').freqstr