Remove unnecessary note for primary_key in the guide

guides/source/active_record_migrations.md

@@ -352,10 +352,10 @@ end
 which creates a `products` table with a column called `name`.
 
 By default, `create_table` will create a primary key called `id`. You can change
-the name of the primary key with the `:primary_key` option (don't forget to
-update the corresponding model) or, if you don't want a primary key at all, you
-can pass the option `id: false`. If you need to pass database specific options
-you can place an SQL fragment in the `:options` option. For example:
+the name of the primary key with the `:primary_key` option  or, if you don't
+want a primary key at all, you can pass the option `id: false`. If you need to
+pass database specific options you can place an SQL fragment in the `:options`
+option. For example:
 
 ```ruby
 create_table :products, options: "ENGINE=BLACKHOLE" do |t|