Git commits in Moodle 3.8.x by Marcus Boon

commit 0b62a26225bac4d49ef394bafb52dacc6c76e47a
Author: Marcus Boon <marcus@catalyst-au.net>
Date:   Thu, 09 Apr 2020 11:00:29 +0800
Tag:    v3.8.4

MDL-68388 core_grades: Use MUC for grade letters