This addresses part of the goal of [ENG-9557](https://linear.app/comm/issue/ENG-9557/prevent-some-robotext-from-bumping-last-message-in-thin-threads).
Note that we'll have to continue setting the thread to unread for reactions to your own messages, as those generate a notif. More context [here](https://linear.app/comm/issue/ENG-9557/prevent-some-robotext-from-bumping-last-message-in-thin-threads#comment-2d9aa66f).
Depends on D13919