Git commits in Moodle 3.8.3 by Ferran Recio

commit 8aa0b41e9bd4140049e69c59546ca86ba7f0c1c9
Author: Ferran Recio <ferran@moodle.com>
Date:   Mon, 04 May 2020 22:41:12 +0800
Tag:    v3.8.3

MDL-68430 filter_mathjaxloader: update default CDN to 2.7.8