DOC: Enforce Numpy Docstring Validation for freqstr, nanos, and rule_code methods
Dosctring Validation for freqstr, nanos, and rule_code methods of pandas.tseries.offsets Week, WeekOfMonth, YearBegin, and YearEnd classes.

- [x] fixes #58536
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added/modified dosctrings for freqstr, nanos, and rule_code methods of pandas.tseries.offsets Week, WeekOfMonth, YearBegin, and YearEnd classes in the pandas/_libs/tslibs/offsets.pyx file.
- [x] Deleted the relevant names from code_checks.sh
- [x] Tested doctstring validation for all the above methods.

Thanks @Siniade 