Update maven to 3.6.2 and gradle to 5.6.x on java8 build image
Update maven to 3.6.2 and gradle to 5.6.x on java8 build image

lambci/docker-lambda,lambci/docker-lambda,lambci/docker-lambda,lambci/docker-lambda,lambci/docker-lambda,lambci/docker-lambda,lambci/docker-lambda