Fix migration typo (missing keyword foreign_key)

Also set `primary_taxon_id` column type to be integer to match `spree_taxons.id`

Author: chaimann

core/db/migrate/20250207104016_add_primary_taxon_to_products.rb

@@ -1,7 +1,7 @@
 class AddPrimaryTaxonToProducts < ActiveRecord::Migration[7.0]
   def change
     change_table :spree_products do |t|
-      t.references :primary_taxon, { to_table: :spree_taxons }
+      t.references :primary_taxon, type: :integer, foreign_key: { to_table: :spree_taxons }
     end
   end
 end