MDL-77346 mod_workshop: Added missing class properties

In PHP 8.2 and later, setting a value to an undeclared class property is
deprecated and emits a deprecation notice.
So we need to add missing class properties that still need to be declared.

mod/workshop/allocation/random/lib.php

@@ -731,6 +731,8 @@ class workshop_random_allocator_setting {
     public $assesswosubmission;
     /** @var bool add self-assessments */
     public $addselfassessment;
+    /** @var bool scheduled allocation status */
+    public $enablescheduled;
 
     /**
      * Use the factory method {@link self::instance_from_object()}