Ensure reproduce_comparison Compare stage cleans WS of sbom and other prepare stage artifacts

[andrew-m-leonard]

Occasionally the reproduce_comparison fails the Compare stating:

Only in /home/jenkins/workspace/jdk21-linux-x64-temurin_reproduce_compare/original: OpenJDK21U-sbom_x64_linux_hotspot_2023-09-04-14-43.json

This is because the Prepare stage where it extracted the sbom, was not cleaned.

Fixes #805

[github-actions]

Thank you for creating a pull request!

Please check out the information below if you have not made a pull request here before (or if you need a reminder how things work).

Code Quality and Contributing Guidelines

If you have not done so already, please familiarise yourself with our Contributing Guidelines and Code Of Conduct, even if you have contributed before.

Tests

Github actions will run a set of jobs against your PR that will lint and unit test your changes. Keep an eye out for the results from these on the latest commit you submitted. For more information, please see our testing documentation.

In order to run the advanced pipeline tests (executing a set of mock pipelines), it requires an admin to post run tests on this PR.
If you are not an admin, please ask for one's attention in #infrastructure on Slack or ping one here.
To run full set of tests, use "run tests"; a subset of tests on specific jdk version, use "run tests quick 11,21"