Apply Style/CollectionMethods rubocop rule

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

app/helpers/valuation_helper.rb

@@ -5,11 +5,11 @@ module ValuationHelper
 
   def valuator_select_options
     Valuator.order("description ASC").order("users.email ASC").includes(:user).
-             collect { |v| [v.description_or_email, "valuator_#{v.id}"] }
+             map { |v| [v.description_or_email, "valuator_#{v.id}"] }
   end
 
   def valuator_group_select_options
-    ValuatorGroup.order("name ASC").collect { |g| [g.name, "group_#{g.id}"] }
+    ValuatorGroup.order("name ASC").map { |g| [g.name, "group_#{g.id}"] }
   end
 
   def explanation_field(field)