MDL-58412 mod_feedback: Remove access control in get_items

This function it is used for printing the list of questions.
The feedback preview doesn’t have any access restriction, you can see
the list of questions at any time.

mod/feedback/classes/external.php

@@ -422,7 +422,6 @@ class mod_feedback_external extends external_api {
         $warnings = array();
 
         list($feedback, $course, $cm, $context) = self::validate_feedback($params['feedbackid']);
-        self::validate_feedback_access($feedback,  $course, $cm, $context);
 
         $feedbackstructure = new mod_feedback_structure($feedback, $cm, $course->id);
         $returneditems = array();