The Carlton and Floss dance emotes are no longer available in Forza Horizon 4 following changes made to the game as part of todays big Series 5 update. Although publisher Microsoft wont say why it removed the emotes, both dances are the subjects of lawsuits against publisher Epic Games for using them in the mega-popular game Fortnite.
Source: N4G PC Microsoft Removes Carlton, Floss Dances From Forza Horizon 4