RFR: Update to JUnit 5.5.2

[Erik Helin]

Hi all,

this small patch updates the JUnit dependency to 5.5.2.

## Testing
- [x] `sh gradlew test` passes on Linux x86_64

Thanks,
Erik

----------------

Commits:
 - d968638a:	Update to JUnit 5.5.2

Pull request:
https://git.openjdk.java.net/skara/pull/138

Webrev:
https://webrevs.openjdk.java.net/skara/138/webrev.00

Patch:
https://git.openjdk.java.net/skara/pull/138.diff

Fetch command:
git fetch https://git.openjdk.java.net/skara pull/138/head:pull/138