Git commits in Moodle 3.9.15 by Laurent David

commit 32ee8e3d34359ceb20894a7b5bd4b42ddb4f6418
Author: Laurent David <lmedavid@gmail.com>
Date:   Mon, 16 May 2022 13:35:21 +0800
Tag:    v3.9.15

MDL-74473 core_analytics: Upgrade ML Backend to 2.6.6