Sphinx: Mocking numpy.random breaks scipy 1.4.1 imports

Created by: JoschD

And it seems, the bug it was fixing before is no longer present in newer numpy versions. Should just be removed from config.py in doc folder.

Only a problem when travis generates the doc. Imports work fine with scipy 1.3.0 which is why we haven't seen this problem before.

Thanks @mihofer and @fsoubelet for noticing