Fix cb's janky level name in WorldCreator (#7851)

patches/api/Item-Rarity-API.patch

@@ -65,9 +65,9 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 --- a/src/main/java/org/bukkit/UnsafeValues.java
 +++ b/src/main/java/org/bukkit/UnsafeValues.java
 @@ -0,0 +0,0 @@ public interface UnsafeValues {
-      * @throws IllegalArgumentException if there isn't a registry for that type
+      * Just don't use it.
       */
-     <T extends Keyed> @org.jetbrains.annotations.NotNull Registry<T> registryFor(Class<T> classOfT);
+     @org.jetbrains.annotations.NotNull String getMainLevelName();
 +
 +    /**
 +     * Gets the item rarity of a material. The material <b>MUST</b> be an item.