prevents mindswaping into ghost poly (#62554)

About The Pull Request

Closes #62465

Also makes ghost poly technically designated as a boss in the code as their sentience type, as far as I can tell this doesn't actually change anything other than the ability to make it sentient, but it also makes sense for a creature effectively incapable of death to be designated as a boss in the code.
Why It's Good For The Game

As funny as it is, mindswapping (blood into a rainbow slime extract gives you a mindswap potion) into ghost poly, or otherwise making ghost poly sentient, is an exploit that should be patched. Ghost poly is as fast as a ghost, can move through walls, has godmode, and if you give it a fugu gland it can beat people up. It can also pick up things, such as the nuke disk, which would make nukeops rounds pretty unfair and unfun.
Changelog

cl
fix: Aspiring xenobiologists and ambitious wizards can no longer mindswap into ghost poly or otherwise make them sentient in an attempt to gain godmode + ghost speed + the ability to go through walls.
/cl

code/modules/mob/living/simple_animal/parrot.dm

@@ -976,6 +976,7 @@ GLOBAL_LIST_INIT(strippable_parrot_items, create_strippable_list(list(
 	color = "#FFFFFF77"
 	speak_chance = 20
 	status_flags = GODMODE
+	sentience_type = SENTIENCE_BOSS //This is so players can't mindswap into ghost poly to become a literal god
 	incorporeal_move = INCORPOREAL_MOVE_BASIC
 	butcher_results = list(/obj/item/ectoplasm = 1)