Ensure `donor_import.py` is run on archweb

Seems like our donation page is not updating with new names anymore. There is a script which is suppose to run and read from a mailbox, but I don't think (and freswa has confirmed) that this might have been fixed again when splitting off services into VPSes.

https://github.com/archlinux/archweb/blob/master/main/management/commands/donor_import.py