Remove test result combination script

[nebelsprachen]

Status

Ready for review

Description of Changes

Removes script that is no longer used

Fixes #4746

Changes proposed in this pull request:

Testing

How should the reviewer test this PR?

Deployment

Any special considerations for deployment? Consider both:

1. Upgrading existing production instances.
2. New installs.

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make test) pass in the development container

If you made changes to securedrop-admin:

• Linting and tests (make -C admin test) pass in the admin development container

If you made changes to the system configuration:

• Configuration tests pass

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

If you made changes to documentation:

• Doc linting (make docs-lint) passed locally

If you added or updated a code dependency:

Choose one of the following:

• I have performed a diff review and pasted the contents to the packaging wiki
• I would like someone else to do the diff review

[emkll]

Looks like we also aren't using the script it's invoking, do you think it makes sense to remove that one as well? https://github.com/joaedwar/securedrop/blob/4746_Test-scripts/devops/scripts/combine-junit.py

It seems like we forgot to clean this up when migrating platforms for CI in https://github.com/freedomofpress/securedrop/pull/3909/files

[nebelsprachen]

@emkll Please review. I removed the suggested file.

[emkll]

Thanks @joaedwar !