replace invoice_number method with delegate

app/models/invoice/data_presenter.rb

@@ -5,6 +5,7 @@ class Invoice
     attr_reader :invoice
 
     delegate :data, :date, to: :invoice
+    delegate :number, to: :invoice, prefix: true
 
     FINALIZED_NON_SUCCESSFUL_STATES = %w(canceled returned).freeze
 
@@ -86,10 +87,6 @@ class Invoice
       date
     end
 
-    def invoice_number
-      invoice.number
-    end
-
     def paid?
       data[:payment_state] == 'paid' || data[:payment_state] == 'credit_owed'
     end