Git commits in Moodle 3.9.3 by Dan Marsden

commit 4727970abd79bbaafb1de35dce1b617f3270a2de
Author: Dan Marsden <dan@danmarsden.com>
Date:   Fri, 03 Jul 2020 07:23:17 +0800
Tag:    v3.9.3

MDL-69641 grade: fix slow query.