Fix SS06 formatting errors
SS06 (Summary should fit in a single line) errors fixed (#29254) for the following:

```
 pandas.DataFrame.slice_shift
 pandas.DataFrame.to_period
 pandas.DataFrame.plot
 pandas.DataFrame.sparse.density
 pandas.DataFrame.style
 pandas.Series.as_blocks
 pandas.Series.ix
 pandas.Series.ptp
 pandas.DataFrame.as_blocks
 pandas.DataFrame.ix
```
Validated with `python scripts/validate_docstrings.py`

Also referencing issue: #27977
Hi @WillAyd, added the changes you suggested. Great thanks @profwacko !