Change parameter type from int to constant variable

lib.php

@@ -37,7 +37,7 @@ function local_sembasednav_extend_navigation(global_navigation $navigation)
     $PAGE->requires->js_call_amd('local_sembasednav/sembasednav', 'closeAllChildNodes', [$myCoursesNode->key]);
 
     // type() needed to get an array for usort - navigation_node_collection by itself is not sortable
-    $courses = $myCoursesNode->children->type(20);
+    $courses = $myCoursesNode->children->type(navigation_node::TYPE_COURSE);
 
     // Nodes that are excluded from max semester count - will always be shown
     $noSemesterAssignedName = get_config('sembasednav', 'setting_nosemestername');