What I expected to happen was...:
Don't see Shulker spawning in peaceful difficulty

What actually happened was...:
Shulker spawned in peaceful difficulty and don't dispawn when i change the game difficulty Easy/Medium/Hard to peaceful

Steps to Reproduce:

Put yout game in Easy/Medium/Hard difficulty and spawn a Shulker with his egg, them change to peaceful difficulty and he won't dispawn like the other hostile mobs.

Shulkers also naturally spawn in end citys in peaceful difficulty and can attack you.