RFR: Update to Gradle 5.6.2

[Erik Helin]

Hi all,

this patch updates Gradle to version 5.6.2.

## Testing
- [x] `sh gradlew images` produces correct images
- [x] `sh gradlew test` passes
- [x] `sh gradlew reproduce` passes

Thanks,
Erik

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

Commits:
 - 058e5b77:	Update to Gradle 5.6.2

Pull request:
https://git.openjdk.java.net/skara/pull/140

Webrev:
https://webrevs.openjdk.java.net/skara/140/webrev.00

Patch:
https://git.openjdk.java.net/skara/pull/140.diff

Fetch command:
git fetch https://git.openjdk.java.net/skara pull/140/head:pull/140