Revert "Fixed: gantt broken when no due date on project issues and versions."

It broke the tests for overdue projects and isn't a good way to fix #6350
because it makes an assumption that a project is due Today and will still
error if issue tracking is disabled.

This reverts commit a7fd592db4. (r4178)

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4184 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/project.rb

@@ -432,14 +432,13 @@ class Project < ActiveRecord::Base
     end
   end
 
-  # The latest due date of an issue or version, otherwise today
+  # The latest due date of an issue or version
   def due_date
     if module_enabled?(:issue_tracking)
       [
        issues.maximum('due_date'),
        shared_versions.collect(&:effective_date),
-       shared_versions.collect {|v| v.fixed_issues.maximum('due_date')},
-       Date.today
+       shared_versions.collect {|v| v.fixed_issues.maximum('due_date')}
       ].flatten.compact.max
     end
   end