MXNet nightly numpy dependency bump breaks stuff

[leezu]

Description

Somewhere between today and 11th July, MXNet pre-release on Pypi declared to rely on numpy<2.0.0,>1.16.0 instead of numpy<1.15.0,>=1.8.2, thus bringing with it some breaking changes:

In particular, we're hit by:

Unpickling while loading requires explicit opt-in

The functions load, and lib.format.read_array take an
allow_pickle keyword which now defaults to False in response to
CVE-2019-6446 https://nvd.nist.gov/vuln/detail/CVE-2019-6446_.

.. currentmodule:: numpy.random.mtrand

as it breaks ./scripts/bert/run_pretraining.py