Remove useless customer loading and clarify name

The method `associate_customer` only loads a customer but doesn't
actually associate one. So the deleted line doesn't have any effect.

The intention was to reset the customer after switching shops but the
before_validation logic on the order model takes care of that already.

I'm renaming this private method here for clarity.

app/models/spree/order.rb

@@ -717,7 +717,7 @@ module Spree
       (user&.email || email)&.downcase
     end
 
-    def associate_customer
+    def find_customer
       return customer if customer.present?
 
       Customer.of(distributor).find_by(email: email_for_customer)
@@ -738,7 +738,7 @@ module Spree
     end
 
     def ensure_customer
-      self.customer = associate_customer || create_customer
+      self.customer = find_customer || create_customer
     end
 
     def update_adjustment!(adjustment)

app/services/order_cart_reset.rb

@@ -30,7 +30,6 @@ class OrderCartReset
     return unless current_user
 
     order.associate_user!(current_user) if order.user.blank? || order.email.blank?
-    order.__send__(:associate_customer) if order.customer.nil? # Only associates existing customers
   end
 
   def reset_order_cycle(current_customer)