Edit docs to say mail_fetcher runs every 5 minutes
Edit docs to say mail_fetcher runs every 5 minutes

In `config/schedule.rb` there's code that clearly says
`script/mail_fetcher` is run every 5 minutes:

```
every 5.minutes do
  run_script "mail_fetcher"
end
```

Trello card: https://trello.com/c/NbgFTMR4/2022-5-alert-on-fact-check-replies-that-werent-parsed

alphagov/publisher,alphagov/publisher,alphagov/publisher