Update config to point at modern custom field article.

Summary: Fixes T5215. This mentions an old article name.

Test Plan: Read config option.

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5215

Differential Revision: https://secure.phabricator.com/D9331

Author: epriestley

src/applications/maniphest/config/PhabricatorManiphestConfigOptions.php

@@ -218,9 +218,9 @@ public function getOptions() {
         ->setSummary(pht("Custom Maniphest fields."))
         ->setDescription(
           pht(
-            "Array of custom fields for Maniphest tasks. For details on ".
-            "adding custom fields to Maniphest, see 'Maniphest User Guide: ".
-            "Adding Custom Fields'."))
+            'Array of custom fields for Maniphest tasks. For details on '.
+            'adding custom fields to Maniphest, see "Configuring Custom '.
+            'Fields" in the documentation.'))
         ->addExample(
           '{"mycompany:estimated-hours": {"name": "Estimated Hours", '.
           '"type": "int", "caption": "Estimated number of hours this will '.