Remove duplicate definition of payment providers

app/controllers/spree/admin/payment_methods_controller.rb

@@ -117,7 +117,7 @@ module Spree
       end
 
       def validate_payment_method_provider
-        valid_payment_methods = Spree::PaymentMethod.providers.map(&:to_s)
+        valid_payment_methods = PAYMENT_METHODS.keys
         return if valid_payment_methods.include?(params[:payment_method][:type])
 
         flash[:error] = Spree.t(:invalid_payment_provider)
@@ -133,7 +133,7 @@ module Spree
       end
 
       def load_providers
-        providers = Gateway.providers.sort_by(&:name)
+        providers = PAYMENT_METHODS.values.sort_by(&:name)
 
         unless show_stripe?
           providers.reject! { |provider| stripe_provider?(provider) }

app/models/spree/payment_method.rb

@@ -52,14 +52,6 @@ module Spree
         .where(environment: [Rails.env, "", nil])
     }
 
-    def self.providers
-      [
-        Spree::PaymentMethod::Check,
-        Spree::Gateway::StripeSCA,
-        Spree::Gateway::PayPalExpress,
-      ]
-    end
-
     def configured?
       !stripe? || stripe_configured?
     end