https://www.pcgamer.com/forza-horizon-4-drops-the-carlton-and-floss-emotes/

Epic Games is facing lawsuits over the presence of emotes including the Floss and the Carlton in Fortnite, without credit or compensation going to the people who created or popularized them. And maybe it's coincidence or maybe it's not, but those same dances have now been removed from Forza Horizon 4. 

The change comes as part of the Forza Horizon 4 Series 5 update, which makes a number of fairly significant additions to the game including a Mitsubishi Motors car pack, a new free-for-all Adventure and Horizon Story missions, and new seasonal events, cars, and more. But it's the very last entry in the list of smaller changes and fixes in the full patch notes that's of particular interest: "The 'Carlton' and 'Floss' avatar emotes are no longer available."