DOC: fix EX02 errors in docstrings
Related to the issue #51236

This PR enables functions:
`pandas.core.groupby.DataFrameGroupBy.take`
`pandas.Timestamp.fromtimestamp`
> thanks @natmokval - looks like `DataFrameGroupBy.take` was already passing then?
> 
It was fixed when I deleted `pandas.core.groupby.SeriesGroupBy.take` function from the ignore list in the previous PR #51432. It looks like the same changes in `pandas/core/groupby/generic.py` are required.