Fix Style/ReductantReturn rubocop

Exclusions from .rubocop_todo.yml deleted.This cop checks for redundant return expressions.
Fixes #1824

app/helpers/format_helper.rb

@@ -101,17 +101,17 @@ module FormatHelper
 
   def icon_for_todo(bool)
     if bool
-      return 'fa fa-check'
+      'fa fa-check'
     else
-      return 'fa fa-times'
+      'fa fa-times'
     end
   end
 
   def class_for_todo(bool)
     if bool
-      return 'todolist-ok'
+      'todolist-ok'
     else
-      return 'todolist-missing'
+      'todolist-missing'
     end
   end