[scikit-learn] Deleting old RCs from PyPI

[Jeremie du Boisberranger]

Hi everyone,

During the last release we reached our project limit size on PyPI. 
Although we've been able to increase this limit, we thought that it 
would be a good idea to make some space. As a first step, we plan to 
remove all release candidates (RCs) of previous releases. These should 
not be downloaded by anyone at this point. If you need these old RCs, 
please tell us quickly before we delete them because it will be permanent.

We also plan to remove all releases but the last from testpypi. Same, if 
you need them please tell us quickly.

Have a good day,

Jérémie