Removed invalid association IssueCustomField#issue_custom_values (#32431).

Patch by Akira Matsuda.

git-svn-id: http://svn.redmine.org/redmine/trunk@19061 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/issue_custom_field.rb

@@ -20,7 +20,6 @@
 class IssueCustomField < CustomField
   has_and_belongs_to_many :projects, :join_table => "#{table_name_prefix}custom_fields_projects#{table_name_suffix}", :foreign_key => "custom_field_id", :autosave => true
   has_and_belongs_to_many :trackers, :join_table => "#{table_name_prefix}custom_fields_trackers#{table_name_suffix}", :foreign_key => "custom_field_id", :autosave => true
-  has_many :issues, :through => :issue_custom_values
 
   safe_attributes 'project_ids',
                   'tracker_ids'