Fix Jenkins pod not starting since Kubernetes node pool upgrade

The pool-4-platform-build node pool was automatically upgraded by Kubernetes on 2021-09-01T20:51:53, triggering pod restarts.

Since the jenkins/jenkins:lts image now uses JDK 11 by default, the following JVM options are no longer valid:

    -XX:+UnlockExperimentalVMOptions
    -XX:+UseCGroupMemoryLimitForHeap

and prevent the JVM from starting:

Unrecognized VM option 'UseCGroupMemoryLimitForHeap'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit