remove the extra comma in association_basics.md

guides/source/association_basics.md

@@ -1831,7 +1831,7 @@ The `limit` method lets you restrict the total number of objects that will be fe
 class Author < ApplicationRecord
   has_many :recent_books,
     -> { order('published_at desc').limit(100) },
-    class_name: "Book",
+    class_name: "Book"
 end
 ```