Java API example is broken

[Sophietje]

We need to look into the example in examples/java-api to see whether we can fix it or want to remove this example.

[bnouwt]

Remove it, for it is no longer working. Maybe in the future replace it with a simple Java example, but until then we can look at other Java examples like the weather-knowledge-base, pushpull-knowledge-base or storage-knowledge-base.