I have already reported this issue but it was deemed invalid because I reported it along with other bugs.
Some spawn eggs have the old spotted variant image instead of the new ones, all the eggs with this issue are: Horse Spawn Egg, Donkey Spawn Egg, Mule Spawn Egg, Skeleton Horse Spawn Egg, Zombie Horse Spawn Egg, And Drowned Spawn Egg.
Images below.
This is on a world without Experimental features or any resource or Behavior packs, Although this bug does apply to worlds with Experimental features.
Please attach a screenshot of Settings > Global Resources and the resource packs tab of your world.