Git commits in Moodle 3.7.5 by Marina Glancy

commit 6b502fbc2b76f2a129919d01e191a3f7d1095d24
Author: Marina Glancy <marina@moodle.com>
Date:   Wed, 04 Mar 2020 01:30:06 +0800
Tag:    v3.7.5

MDL-56287 gradereport_history: Separate groups queries improved