[Integrated] RFR: Update to JUnit 5.5.2

[duke]

Changeset: 36cc70a2
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-09-18 07:24:39 +0000
URL:       https://git.openjdk.java.net/skara/commit/36cc70a2

Update to JUnit 5.5.2

Reviewed-by: rwestberg

! build.gradle