mod_http_oauth2: Use new mod_cron API for periodic cleanup Less frequent but this isn't that important after all since, as the comment states, expired codes are not usable anyway. They're also not that large so memory usage probably doesn't matter.

This module helps make BOSH and WebSocket connection endpoints
discoverable via the HTTP method described in
[XEP-0156](https://xmpp.org/extensions/xep-0156.html#http).