Resolve "Globale Einstellung SHOW_RELEASE_NOTES wird nicht verwendet"

Closes #4835

Merge request studip/studip!3621

db/migrations/6.0.30_remove_obsolete_release_notes_config.php

+<?php
+
+final class RemoveObsoleteReleaseNotesConfig extends Migration
+{
+    public function description()
+    {
+        return 'removes the obsolete global config entry SHOW_RELEASE_NOTES';
+    }
+
+    public function up()
+    {
+        DBManager::get()->exec("DELETE `config`, `config_values`
+                  FROM `config`
+                  LEFT JOIN `config_values` USING (`field`)
+                  WHERE `field`  = 'SHOW_RELEASE_NOTES'");
+    }
+
+}