Apply Style/CollectionMethods rubocop rule

We were already using `map` and `reduce` almost everywhere.

app/helpers/admin_helper.rb

@@ -83,9 +83,7 @@ module AdminHelper
   end
 
   def admin_select_options
-    Administrator.with_user
-                 .collect { |v| [v.description_or_name, v.id] }
-                 .sort_by { |a| a[0] }
+    Administrator.with_user.map { |v| [v.description_or_name, v.id] }.sort_by { |a| a[0] }
   end
 
   def admin_submit_action(resource)