Update javadoc

Author: NichtStudioCode

invui/src/main/java/xyz/xenondevs/invui/item/ItemProvider.java

@@ -11,7 +11,7 @@
 public interface ItemProvider extends Supplier<ItemStack>, Cloneable {
 
     /**
-     * An {@link ItemProvider} for an {@link ItemStack}.
+     * An {@link ItemProvider} for an empty {@link ItemStack}.
      */
     ItemProvider EMPTY = new ItemWrapper(ItemStack.empty());