Update more_bossbars.json

Author: LiteraDev

data/literagame/advancements/more_bossbars.json

@@ -8,7 +8,7 @@
             "color": "gold"
         },
         "icon": {
-            "item": "minecraft:wither_skeleton_skull"
+            "item": "minecraft:piglin_head"
         },
         "frame": "task",
         "show_toast": true,
@@ -26,4 +26,4 @@
         ]
     ],
     "parent": "literagame:root"
-}
+}