Manage the render of the price field on admin budget headings

Avoid displaying the price in admin budget headings section
and avoid fill the field 'price' in admin budget headings form
when the budget has been checked with hide_money field.

app/models/budget.rb

@@ -230,6 +230,10 @@ class Budget < ApplicationRecord
     voting_style == "approval"
   end
 
+  def show_money?
+    !hide_money?
+  end
+
   private
 
     def generate_phases