Convert route to resource

I don't know why the route helper now has "index" in the name.

app/views/spree/admin/shared/_product_sub_menu.html.haml

@@ -5,4 +5,4 @@
     = tab :variant_overrides, url: main_app.admin_inventory_path, match_path: '/inventory'
     = tab :import, url: main_app.admin_product_import_path, match_path: '/product_import'
     - if feature?(:admin_style_v3, spree_current_user)
-      = tab :products_v3, url: main_app.admin_products_v3_path
+      = tab :products_v3, url: main_app.admin_products_v3_index_path

config/routes/admin.rb

@@ -70,7 +70,7 @@ Openfoodnetwork::Application.routes.draw do
     post '/product_import/reset_absent', to: 'product_import#reset_absent_products', as: 'product_import_reset_async'
 
     constraints FeatureToggleConstraint.new(:admin_style_v3) do
-      get '/products_v3', to: 'products_v3#index'
+      resources :products_v3, only: :index
     end
 
     resources :variant_overrides do