Improve upgrade status for CCK modules

change to:

    case 'cck':
    case 'content':
      $projects[$project]['in_core_since'] = '7.x';
      $projects[$project]['in_core_note'] = t('You still need <a href="@cck-url">CCK</a> to upgrade your fields to Drupal 7. Additional bundled modules have been moved out of CCK: for Node References and User References, see References module; for Field Groups, consult Field Group module; for Permissions in fields, check Field Permissions module. There is an overall CCK to field <a href="@upgrade-issue-url">upgrade path discussion</a>. Contributed modules may use <a href="@field-convert-url">Field converter</a> as dependency to properly upgrade their non-field data to fields. Custom programmed field type modules, which may be obsolete now, might be easier to upgrade using <a href="@migrate-url">Migrate</a> module.', array(
        '@upgrade-issue-url' => 'http://drupal.org/node/366364',
        '@cck-url' => 'http://drupal.org/project/cck',
        '@references-url' => 'http://drupal.org/project/references',
        '@field-group-url' => 'http://drupal.org/project/field_group',
        '@field-permissions-url' => 'http://drupal.org/project/field_permissions',
        '@field-convert-url' => 'http://drupal.org/project/field_convert',
        '@migrate-url' => 'http://drupal.org/project/migrate',
      ));
      break;

Directly related to #903060: Better handling for partially in core cases, tempted to mark as duplicate, but leaving as-is for now.

Triaging all Drupal 6 Upgrade Status issues. As Drupal 6 is no longer supported by this module and this is only relevant to the Drupal 6 version, closing this.