SpringBoot Use Gradle's task configuration avoidance APIs in the main reference docs

see https://github.com/spring-projects/spring-boot/pull/29762 see https://docs.gradle.org/7.0/userguide/task_configuration_avoidance.html

Comment From: larsgrefer

I've updated the PR based on your comments.

Comment From: wilkinsona

Thanks very much, @larsgrefer.