Git commits in Moodle 3.9.3 by Dani Palou

commit e7bb7aa9a2b83f4c98da0cf355bebc28bad1fae0
Author: Dani Palou <dani@moodle.com>
Date:   Wed, 23 Sep 2020 17:18:28 +0800
Tag:    v3.9.3

MDL-68098 tests: Reset FILTERLIB_PRIVATE after tests


commit 7aca3ebb3c2e4f6eff92c128edf70a3159c0c673
Author: Dani Palou <dani@moodle.com>
Date:   Fri, 04 Sep 2020 15:25:15 +0800
Tag:    v3.9.3

MDL-68098 ws: Add unit tests to test mathjax in WS


commit fba96f096bfa39e8255b180b41ad287679268762
Author: Dani Palou <dani@moodle.com>
Date:   Fri, 04 Sep 2020 15:21:45 +0800
Tag:    v3.9.3

MDL-68098 ws: Fix WebServices broken by filters HTML