DEPR: index argument to SparseArray

It's out of place with the other array types, and not used in many places

```python
In [1]: import pandas as pd

In [2]: pd.SparseArray(1, index=[0, 1, 2])
Out[2]:
[1, 1, 1]
Fill: 0
IntIndex
Indices: array([0, 1, 2], dtype=int32)
```