Modified `generatesNotifs` in `reaction-message-spec` to return `notif` if the reaction `action` is equal to `add_reaction` and `rescind` if the reaction `action` is equal to `remove_reaction`
**Won't land this diff until the entire stack for this task is accepted and ready to land. The current changes would cause notifs to no longer send if a user were to unlike a message**
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Linear Task: [[ https://linear.app/comm/issue/ENG-2644/rescind-a-reaction-message-notif-with-a-remove-action-from-the | ENG-2644 ]]