chore: update supervisor plugin example jenkins template

[dilyar85]

Description

This PR updates the Supervisor builder example template to install a newer JDK version.
The current JDK version (11) is no longer supported by the latest Jenkins release (2.426.1):

packer@jenkins-test:~$ jenkins
Running with Java 11 from /usr/lib/jvm/java-11-openjdk-amd64, which is older than the minimum required version (Java 17).
Supported Java versions are: [17, 21]

Testing

The Packer command ran successfully using the updated template file:

$ packer build jenkins-template.pkr.hcl
vsphere-supervisor.vm: output will be in this color.

==> vsphere-supervisor.vm: Creating temporary RSA SSH key for instance...
    vsphere-supervisor.vm: Connecting to Supervisor cluster...
    ...
    vsphere-supervisor.vm: Source VM is now ready in Supervisor cluster
    ...
==> vsphere-supervisor.vm: Provisioning with shell script: /var/folders/nf/cndlm4ts2bd9jz3dd667jfb80000gr/T/packer-shell3086856209
    ...
==> vsphere-supervisor.vm: + sudo apt-get -qq -o Acquire::ForceIPv4=true install -f -y ca-certificates openjdk-21-jre-headless
    ...
    vsphere-supervisor.vm: Completed sample-job #1 : SUCCESS
    vsphere-supervisor.vm: Skip cleaning up the VirtualMachinePublishRequest object as specified in config
    vsphere-supervisor.vm: Skip cleaning up the source objects as specified in config
    vsphere-supervisor.vm: Build 'vsphere-supervisor' finished successfully.
Build 'vsphere-supervisor.vm' finished after 3 minutes 17 seconds.

==> Wait completed after 3 minutes 17 seconds

==> Builds finished but no artifacts were created.

Reference

https://www.jenkins.io/doc/book/platform-information/support-policy-java/#java-support-policy

[akutz]

Lgtm, thanks @dilyar85 !

[nywilken]

LGTM! Thank you for keeping the examples updated.