Trivy detected vulnerable versions of Jetty

In the following PR we added suppressions for vulnerabilities in org.eclipse.jetty:jetty-security and org.eclipse.jetty:jetty-server:

- https://github.com/gchq/sleeper/issues/7735
- https://github.com/gchq/sleeper/pull/7736

It doesn't look like this was the correct solution, as there shouldn't be vulnerable versions of those in our images.

There's also no comment on the suppressions for these. We need to look into why these vulnerabilities are present and either remove them or explain why the suppressions are needed.

#### Possible Maven bug

It's possible this may be a reoccurrence of the following issue:
- https://github.com/gchq/sleeper/issues/6108

That seemed to be a bug in Maven which needed us to specifically correct some transitive test dependencies that were being incorrectly turned into production dependencies:

- https://github.com/gchq/sleeper/pull/6299

That solution is quite brittle because it requires us to continually find occurrences of these dependencies and correct them in the same way. We may be able to upgrade to a later version of Maven that doesn't have this problem, or we might have to specifically correct the new vulnerabilities as well.

Start by reviewing the suppressions added in issue 7735 and pull request 7736, then compare the dependency corrections described in issue 6108 and pull request 6299. Trace why org.eclipse.jetty:jetty-security and org.eclipse.jetty:jetty-server enter the images, and finish by removing unnecessary suppressions or documenting why they remain and verifying the vulnerability scan.

Written by the indexing model from the issue text.