"Herobrine Removed" has been added to a number changelogs. Herobrine is a character from a Minecraft "creepypasta" who looks exactly like the player, but has white eyes. It is said that Herobrine is Notch's dead brother, although Notch said himself that he does not have a dead brother. Herobrine never appeared in the game, and it's likely that this line being added to the changelogs is just a joke with the community.
Contributed by ecylisis