MDL-52206 core: Update new activity_custom_completion

Update the custom_completion classes to accept the new completion
criteria

mod/assign/classes/completion/custom_completion.php

@@ -89,6 +89,7 @@ class custom_completion extends activity_custom_completion {
             'completionview',
             'completionsubmit',
             'completionusegrade',
+            'completionpassgrade',
         ];
     }
 }