DOC: Series.pad has template variables that are not replaced
When looking at the docstring of `pad`:

```
In [21]: pd.Series.pad?
Signature:
pd.Series.pad(
    self: 'FrameOrSeries',
    axis=None,
    inplace: 'bool_t' = False,
    limit=None,
    downcast=None,
) -> 'Optional[FrameOrSeries]'
Docstring:
Synonym for :meth:`DataFrame.fillna` with ``method='ffill'``.

Returns
-------
{klass} or None
    Object with missing values filled or None if ``inplace=True``.
```

Or on the online version: https://pandas.pydata.org/docs/dev/reference/api/pandas.Series.pad.html

There is a ``{klass}`` that has not been properly substituted.