Add missing deprecation for Material#getCreativeCategory (#13686)

Author: Doc94

paper-api/src/main/java/org/bukkit/Material.java

@@ -3556,10 +3556,12 @@ public Multimap<Attribute, AttributeModifier> getDefaultAttributeModifiers(@NotN
     /**
      * Get the {@link CreativeCategory} to which this material belongs.
      *
-     * @return the creative category. null if does not belong to a category
+     * @return the creative category. null if it does not belong to a category
+     * @deprecated items can belong to multiple creative categories and this is no
+     * longer implemented, will always be {@link CreativeCategory#BUILDING_BLOCKS} if not null
      */
-    @Nullable
-    public CreativeCategory getCreativeCategory() {
+    @Deprecated(since = "1.20.6", forRemoval = true)
+    public @Nullable CreativeCategory getCreativeCategory() {
         ItemType type = asItemType();
         return type == null ? null : type.getCreativeCategory();
     }

paper-api/src/main/java/org/bukkit/inventory/ItemType.java

@@ -3281,8 +3281,9 @@ private static <M extends ItemType> M getItemType(@KeyPattern.Value final String
     /**
      * Get the {@link CreativeCategory} to which this item type belongs.
      *
-     * @return the creative category. null if does not belong to a category
-     <!-- * @deprecated use #getCreativeCategories() -->
+     * @return the creative category. null if it does not belong to a category
+     * @deprecated items can belong to multiple creative categories and this is no
+     * longer implemented, will always be {@link CreativeCategory#BUILDING_BLOCKS}
      */
     @Deprecated(since = "1.20.6", forRemoval = true)
     @Nullable CreativeCategory getCreativeCategory();