Fix EX03 errors in generic.py
Fixes EX03 errors in the examples of some docstrings in the script `pandas/core/ generic.py`.

Specifically, flake8 errors in the docstrings of the following functions were corrected:

```
pandas.DataFrame.add_prefix
pandas.DataFrame.add_suffix
pandas.DataFrame.head
pandas.DataFrame.last
pandas.DataFrame.pop
pandas.DataFrame.reindex
pandas.DataFrame.reindex_like
pandas.DataFrame.tail
pandas.DataFrame.take
pandas.DataFrame.to_xarray 
pandas.DataFrame.truncate
pandas.DataFrame.tz_localize
```

Related to #27977 cc @datapythonista 

- [ ] closes #xxxx
- [ ] tests added / passed
- [X] passes `black pandas`
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
