fixup! Test message edits that have broken timestamps
fixup! Test message edits that have broken timestamps

Note that this also fixes something from "test_add_superseding_event"
but rebasing to fix that would cause conflicts so I'm not going to.

freedesktop-unofficial-mirror/telepathy__telepathy-logger,freedesktop-unofficial-mirror/telepathy__telepathy-logger,freedesktop-unofficial-mirror/telepathy__telepathy-logger