mxnet.ndarray.load docs error

## Description
Sphinx throws an error when generating the docs for this function.

## Error
```
/home/ubuntu/incubator-mxnet/python/mxnet/ndarray/__init__.py:docstring of mxnet.ndarray.load:0: WARNING: duplicate object description of mxnet.ndarray.load, other instance in /home/ubuntu/incubator-mxnet/docs/api/python/ndarray/ndarray.md, use :noindex: for one of them
```