This stops using the wsgi module indirection. Which caused unneeded
complication [1].
I think those modules were to match what we do for deposit and swh-web.
Because django's doc mentions wsgi modules [2] [3]
So, in the end, it's not necessary to follow that convention here. That
introduces indirection and unneeded state (which can cause problem).
[1] Related D2101#48716
[2] https://docs.djangoproject.com/en/2.2/howto/deployment/wsgi/gunicorn/
[2] https://docs.djangoproject.com/en/2.2/howto/deployment/wsgi/