presence: Use presence_last_update_id, new in Zulip Server 9.0

[chrisbobbe]

This isn't planned in our initial implementation for presence (#196). See discussion: #api design > presence rewrite @ 💬

Docs:

• Search for "presence_last_update_id:" at https://zulip.com/api/register-queue
• https://zulip.com/api/update-presence#parameter-last_update_id