chore: update deps

[mikaello]

Updating the grafonnet dependency to latest and removing vendor from git history.

[joanlopez]

Honestly, I'm not super familiar with what's recommended in Jsonnet environments.

I have to admit that generally speaking, I don't like vendoring, especially when the programming environment is mature enough. But, I decided to keep the vendor in this case because I have seen large Jsonnet projects using vendoring, where not used for other environments/programming languages, so I guess that it's perhaps a good practice there.

That being said; I'd probably be happy to remove vendor from this example, as it is just an example, and it's correct working is non-critical. But, to do so, shouldn't we update the GitHub Workflow to download the dependencies at deploy time? If so, could you also please update the README.md, and resolve the conflicts accordingly?

If you're too busy, don't worry. I may re-evaluate this in the future. So far I'm already super happy that you already contributed to make the example better 💟