We forgot to apply this change in commit f5f96ba86.
Note that, in this case, executing `proposal_notification.author.email`
in the middle of a test would also result in a database query. For some
reason (probably the same reason why the code that explicitly created
the author was added in this test but not in other moderation tests),
that doesn't seem to happen in other moderation tests, so for now we
aren't changing those ones.
4b3f58cf4c