[#4420] Remove Deliverable#frequency, assumed to be monthly.

app/models/retainer_deliverable.rb

@@ -1,15 +1,13 @@
 # A RetainerDeliverable is an HourlyDeliverable that is renewed at
 # regular calendar periods.  The Company bills a regular number of
 # hours for a hourly rate whereby the budgets are reset over a
-# regular cyclical period (often monthly).
+# regular cyclical period (monthly).
 class RetainerDeliverable < HourlyDeliverable
   unloadable
 
   # Associations
 
   # Validations
-  ValidFrequencies = ["monthly", "quarterly"]
-  validates_inclusion_of :frequency, :in => ValidFrequencies, :allow_nil => true, :allow_blank => true
   
   # Accessors
 
@@ -106,10 +104,6 @@ class RetainerDeliverable < HourlyDeliverable
     end
   end
 
-  def self.frequencies_to_select
-    ValidFrequencies.collect {|f| [l("text_#{f}"), f]}
-  end
-
   private
 
   def shrink_budgets_to_new_period