Git commits in Moodle 3.8.x by Nick Phillips

commit f8621e3d587082b25f795d10c1e1c68c00eaaf68
Author: Nick Phillips <nick.phillips@otago.ac.nz>
Date:   Wed, 04 Mar 2020 11:16:41 +0800
Tag:    v3.8.4

MDL-68103 theme_classic: hidden-print => d-print-none for BS4.