Set default age parameter for User.prune method to 30 days (#41023).

git-svn-id: https://svn.redmine.org/redmine/trunk@22938 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/user.rb

@@ -887,7 +887,7 @@ class User < Principal
     project_ids.map(&:to_i)
   end
 
-  def self.prune(age)
+  def self.prune(age=30.days)
     User.where("created_on < ? AND status = ?", Time.now - age, STATUS_REGISTERED).destroy_all
   end