Clarify FollowEvent creation and usage

Change "not visible in timelines" to "no longer created in timelines"

Currently the docs state that the FollowEvent is not visible in timelines, this is incorrect as I have one in my timeline [Example](https://github.com/thebinarypenguin/guaw/wiki/User-Activity#followevent). However since it's from 2012 I assume the docs should state the the FollowEvent is **no longer** created in timelines.