Fixex Rails/RootPathnameMethods offense

- Cf. Cop doc at https://docs.rubocop.org/rubocop-rails/cops_rails.html#railsrootpathnamemethods

.rubocop_todo.yml

@@ -638,12 +638,6 @@ Rails/ResponseParsedBody:
     - 'spec/controllers/spree/credit_cards_controller_spec.rb'
     - 'spec/controllers/user_registrations_controller_spec.rb'
 
-# Offense count: 1
-# This cop supports unsafe autocorrection (--autocorrect-all).
-Rails/RootPathnameMethods:
-  Exclude:
-    - 'spec/lib/reports/orders_and_fulfillment/order_cycle_customer_totals_report_spec.rb'
-
 # Offense count: 7
 # This cop supports unsafe autocorrection (--autocorrect-all).
 # Configuration parameters: EnforcedStyle.

spec/lib/reports/orders_and_fulfillment/order_cycle_customer_totals_report_spec.rb

@@ -35,7 +35,7 @@ RSpec.describe Reporting::Reports::OrdersAndFulfillment::OrderCycleCustomerTotal
       end
     end
     let(:comparison_report) do
-      File.read(Rails.root.join(report_file_name))
+      Rails.root.join(report_file_name).read
     end
     let(:report_file_name) do
       "spec/fixtures/reports/orders_and_fulfillment/order_cycle_customer_totals_report.csv"