Bug#918044: petsc4py: breaks slepc4py autopkgtests

[Drew Parsons]

Source: petsc4py
Followup-For: Bug #918044

It's the other way around.  slepc4py depends on petsc4py, petsc4py
does not depend on slepc4py.

As far as I can see the tests are working fine.  slepc4py 3.9 requires
petsc4py 3.9, and therefore fails when attempting to install with
petsc4py 3.10.  The versioned dependencies are already there.

The true villain here is numpy, I think.

Drew