DOC: Improve docstring for pandas.Index.repeat
String assigned to ChiPy (Chicago Python Users Group) chapter of the Worldwide Documentation Sprint

While `Index.repeat` does accept `args` and `kwargs`, it does not pass them through to the underlying `numpy` function.

The only additional parameter the numpy function takes is `axis` ([numpy docs](https://docs.scipy.org/doc/numpy/reference/generated/numpy.repeat.html#numpy.repeat)), which is not supported by pandas:

```python
>>> pd.Index([1, 2, 3]).repeat(2, axis=2)
ValueError: the 'axis' parameter is not supported in the pandas implementation of repeat()
```

Should the *args and **kwargs be removed?

Thanks