MDL-32249 completion: Make grade criteria more consistent

Also, round course grades and remove hardcoded string.

Note: This patch also removes the ability to update the course grade
from the completion interface

course/completion.php

@@ -141,16 +141,6 @@ if ($form->is_cancelled()){
     $aggregation->setMethod($data->role_aggregation);
     $aggregation->save();
 
-    // Update course total passing grade
-    if (!empty($data->criteria_grade)) {
-        if ($grade_item = grade_category::fetch_course_category($course->id)->grade_item) {
-            $grade_item->gradepass = $data->criteria_grade_value;
-            if (method_exists($grade_item, 'update')) {
-                $grade_item->update('course/completion.php');
-            }
-        }
-    }
-
     add_to_log($course->id, 'course', 'completion updated', 'completion.php?id='.$course->id);
 
     $url = new moodle_url('/course/view.php', array('id' => $course->id));