Print out newly added buildpack.toml versions

[sophiewigmore]

Summary

As a part of paketo-buildpacks/github-config#329, print out the newly added versions to stdout when running jam update-dependencies so we can easily see the versions that are new in the buildpack.toml.

Use Cases

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).