Remove unnecessary table join

And use Rails syntax for clarity and future extensions.

engines/dfc_provider/app/services/variant_fetcher.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-# Service used to fetch variants related to an entreprise.
+# Service used to fetch variants related to an enterprise.
 # It improves maintenance as it is the central point requesting
 # Spree::Variant inside the DfcProvider engine.
 class VariantFetcher
@@ -10,7 +10,7 @@ class VariantFetcher
 
   def scope
     Spree::Variant.not_master.
-      joins(product: :supplier).
-      where('enterprises.id' => @enterprise.id)
+      joins(:product).
+      where(spree_products: { supplier: @enterprise })
   end
 end