removes heading reference in ballot

heading info is stored per group in ballot_lines

app/models/budget/ballot.rb

@@ -2,7 +2,6 @@ class Budget
   class Ballot < ActiveRecord::Base
     belongs_to :user
     belongs_to :budget
-    belongs_to :heading
 
     has_many :lines, dependent: :destroy
     has_many :investments, through: :lines

app/models/budget/investment.rb

@@ -49,9 +49,6 @@ class Budget
 
     scope :for_render,             -> { includes(heading: :geozone) }
 
-    scope :with_heading,           -> { where.not(heading_id: nil) }
-    scope :no_heading,             -> { where(heading_id: nil) }
-
     before_save :calculate_confidence_score
     before_validation :set_responsible_name