* Update Gradle in generated Java projects from 2.14.1 to 6.0.1
* Upgrade Java 11 native Gradle from 5.5 to 6.0.1
When Java 11 native client library was introduced it was introduced with an overridden version of the Gradle wrapper (5.5 instead of 2.14.1). From looking at that PR, there doesn't appear to be any specific reason for the versions to differ. This removes the only override of the Gradle wrapper so all the Java projects are up to date and shares the same version.
