Use Gradle version 6.0.1

[NikolayS]

I was unable to run it on the latest MacOS (Monterey):

FAILURE: Build failed with an exception.

* What went wrong:
Could not determine java version from '11.0.12'.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

Switching to 6.0.1 helped.