gnu: python-numpy: Fix inputs.

This fixes 2efabc55, where some inputs
have been changed to propagated-inputs, but the propagated-inputs are
still extended from inputs and the inputs are not extended at all.

* gnu/packages/python.scm (python-numpy, python2-numpy)[inputs]:
Extend from python-numpy-bootstrap's package-inputs. [propagated-inputs]:
Extend from python-numpy-bootstrap's package-propagated-inputs.