Make 'actions' and 'predicates' always a list

Seems simpler to understand and a list of one entry behaves exactly the same

public/mcdoc/loot-table-modifier.mcdoc

@@ -2,14 +2,8 @@ use ::java::data::loot::LootPool
 use ::java::data::loot::LootContextType
 
 dispatch minecraft:resource[loot-table-modifier:loot_modifier] to struct {
-    actions: (
-        Action |
-        [Action]
-    ),
-    predicates: (
-        Predicate |
-        [Predicate]
-    ),
+    actions: [Action],
+    predicates: [Predicate],
 }
 
 struct Action {