Unsilence JDK install commands

[native-api]

There's currently an error installing JDK 8 in ARM64 and due to silencing, it's impossible to see what's wrong.

https://travis-ci.community/t/maven-deploy-multiarch/11450/7

Later in the build, the same commands work okay -- so I can't disgnose the problem otherwise.

[native-api]

Alternatively, I know there's a staging environment. If it has Arm64 machines (ideally, from the same pool as production ones), I could tests there if I'm given access.

[native-api]

Failure unrelated, it's the Docker pull limits.