Adds See Also sections to pandas.core.groupby.DataFrameGroupBy.sem, pandas.core.groupby.DataFrameGroupBy.nunique
- [x] Part of issue #60365 
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
 -i "pandas.core.groupby.DataFrameGroupBy.sem SA01" \ 
 -i "pandas.core.groupby.DataFrameGroupBy.nunique SA01" \  Thanks @thedataninja1786 